Can a Christian be a Conservative?

First of all, the historical background of the new testament is one of political oppression, or at least powerlessness. Christ contended with the worldly authorities of the roman emperor and local elites from the day he was born. He was crucified on the behest of local elites. Additionally, we are served with more direct references by Evangelists:

Jesus called them together and said, “You know that those who are regarded as rulers of the Gentiles lord it over them, and their high officials exercise authority over them. <

Mark 10, 42 but also:

And he saith unto him, Out of thine own mouth will I judge thee, thou wicked servant. Thou knewest that I was an austere man, taking up that I laid not down, and reaping that I did not sow: <

in Luke 19,22. Or here in Luke 1,52:

He hath put down the mighty from their seats, and exalted them of low degree.

There are many, many such parts in scriptue, where power and those that wield it are heavily criticized. So I have a hard time believing, that governing a nation state with capital punishment and a border guarded by ICE can call themselves a christian, be they democrat or republican. This in turn informs my interpretation on the more specific "lack of love for the poor" question. Jesus does not think highly of the wealthy, nor does he view wealth as worthy pursuit. In the Acts, we get a glimpse of how economic matters were run in Jerusalem:

And all that believed were together, and had all things common; And sold their possessions and goods, and parted them to all men, as every man had need.

I think this combination of fundamental critique towards power and disdain for wealth points to a societal order completely beyond what is currently offered on either side of the isle.

In summary:

The answer is trivial if we assume that conservatives do care about the poor, so for the sake of the argument we will take the side of your friend and assume that conservatives do not care about the poor.

• Christians care about the poor, but it is not a requirement that you care about the poor to be a Christian.
• Conservatives may not care about the poor, but it is not a requirement that you do not care about the poor to be a conservative.
• Thus, you can be both Christian and conservative.

There are two sides that one needs to look at this from, the political side and the religious side. From the political side, if we were to say that conservatives as a group care for the poor, then it would be an easy answer: yes, you can be a conservative and a Christian.

However, there is strong evidence to suggest that american conservative policies hurt the poor. It is difficult to analyze cause and effect when so many factors are in play, but the data more often than not seems to favor the idea that trickle-down/supply-side economics and a myriad of other policies indirectly fuel income inequality, and hurt the poor more than they help. For the sake of this argument, I will assume that this is correct.

Thus, we reach the conclusion that conservatism in general shows a lack of care for the poor. However, does that mean that you cannot be a conservative if you do care for the poor? No, you absolutely can be a conservative. In america, conservative, republican, and right-wing are all names for one of two main sides, but reality is not a dichotomy. There are so many facets to each side, and you do not need to agree with the entirety of one side or the other—you can pick or choose what to agree with. Once you disagree with enough values of one side you probably shouldn't identify with that side any longer, but unless it's close to a 50%/50% split, you probably fall on one side or the other.

From the religious side: As other answers have pointed out, Christianity advocates that you care for the poor (I don't think this is a controversial take, so I won't elaborate). However, is it a requirement that you care for the poor to be a Christian? I don't think so. Christianity includes many people from many different denominations, and they do not agree on all counts. I think most Christians generally believe that the poor should be cared for, and I think they would advocate that you care for the poor, but I do not think that showing a lack of care for the poor automatically makes you atheist/agnostic.

We have reached the conclusion that borders are fuzzy, definitions are unclear, and it is debatable whether or not conservatism as a whole cares for the poor. Thus, you can be both a Christian and a conservative.

OP, your friend's position is basically:

Conservatives can't call themselves Christian, because conservatives don't care about the poor.

Speaking as a Christian with mostly "progressive" political positions (by US standards), I can say that your friend is wrong on many levels. To name a few (in no particular order):

• Single-sentence "gotcha" statements are rarely an effective basis for genuine discussion of ideas.
• There are some conservatives who appear to genuinely not care about the poor. There are plenty of others who think that caring for the poor is more effective when done with structural changes to make things easier rather than via direct cash transfers, and/or that it should be voluntary and private rather than enforced with the violence of the state, and/or that it's important but other priorities take precedence.
• There are very few people who agree with 100% of the policy platforms of any given political party or ideology from year to year - hence, even if a party had "We don't care about poor people" in so many words as one of their positions, it still wouldn't necessarily say anything about you.
• "You can't call yourself a Christian unless..." is an extremely dicey way to start a sentence. I favor having some kind of concrete definition for clarity - maybe something like "you believe in God and you believe in the redemptive death and resurrection of Jesus Christ" - but there are whole bucketloads of people, historical and contemporary, who identify as Christians but don't agree with one or more of those statements, let alone any more specific ones. Is it right to say you can't be a Christian if you don't follow every commandment? Bad news for a lot of adulterers out there - not to mention people who eat shellfish and work on Sundays.

In short, I think your friend is wrong on the merits, but even before we get to that, they're in no position to tell millions of conservative Christians that they must be wrong about one identity or the other. "Judge not, lest ye be judged," and all that. If they want to say that a specific political position is incompatible with being a good Christian - i.e. that it contradicts a point of theology - then they'd have to make that case, but they clearly haven't done so.

That question can only be answered once the fundamental question has been resolved - "Can a Christian be involved in any kind of politics, as a member of one political party or another?" Only after a Christian's conscience is clear that, yes, he or she can, will the question of which political party to support become necessary to answer. There seems to be an assumption with many Christians that, "Of course we can be a card-carrying supporter of [insert whichever political party here]..."

Biblically, there was no such political system in operation back then as obtains now. Democracy (in an extremely limited, biased way) was invented by the pagan Greeks. Yet to hear some Christians talk, you might think God requires Democracy to rule the world! It has its merits but is hardly much less free from corruption and godlessness than most other political systems. However, the Bible clearly shows God raising up individual people to be actively involved in the politics of Old Testament days. Consider Esther and Daniel.

The New Testament seems to indicate that with Christianity going global, its persecution (largely by global political elements) would increase, raising the matter of neutrality (if not pacifism). Indeed, by the last book of the Bible, political rulers are shown to be puppets of demonic forces leading them on to Armageddon - the precursor is war against God's people. Ultimately, it is war against God and his sovereign rule over his earth. This is what world rulers are heading towards and they are all utterly blind to that.

Individual Christians are told in the N.T. that they are spiritual ambassadors for Christ; they are to live for Christ, and to die for him. All Christians have to promote the ministry of reconciliation:

"...God who reconciled us to Himself through Jesus Christ, and did give to us the ministration of the reconciliation, how that God was, in Christ - a world reconciling to Himself, not reckoning to them their trespasses; and having put in us the word of the reconciliation, in behalf of Christ, then, we are ambassadors, as if God were calling through us, we beseech, in behalf of Christ, 'Be ye reconciled to God'..." (2 Corinthian 5:19-20 Y.L.T.)

No ambassador is entitled to vote or to become involved in the politics of the nation he is appointed to. Neutrality must be maintained, while promoting the interests of the sovereign who appointed him, and of representing his sovereign's kingdom. If those principles are applied by individual Christians, some may see literal application; others may not.

Christians are citizens of heaven, even while we walk as aliens in this world. Yet, to look at many, you would think God has appointed them, and their denomination, to live and die for a politician heading up one particular political party. I've read the book of the Revelation, and I understand who's pulling political strings, and for what end. I know where I stand, happy to do my civic duty where 'Caesar' requires things that do not conflict with God; being a law-abiding, tax-paying, honest individual. And if that isn't good enough for them, or for others... tough.

It boils down to the gospel

The same question would potentially be asked by a conservative about a progressive, so I'm not sure it's a helpful question to be asking. The real key question is this: is the person obeying the gospel? Meaning do they believe in Jesus and have they repented of their sins. If their political ideology, whatever it is, causes them to reject repentance, or if it warps their view of Jesus enough that they do not truly believe, then they're not a Christian. Otherwise if they believe and have repented (note these aren't a one-time thing but are an ongoing state of the heart evidenced by their life as the book of James says), then they are. They might be wrong on some points and thus sinning in ignorance, but they're still a Christian.

Many people aren't 100% a INSERT POLITICAL IDEOLOGY HERE-ive

And besides there are Conservatives and Progressives who don't agree with all parts of their political ideology, but still apply that label to themselves as the one that fits best from a political point of view. It's worth learning what the person actually believes rather than assuming you know them based on a simple label.

Politics is just not so simple as your friend insists. This is a huge subject and there will be many different themes in different answers.

Current Political situation in UK

Here in the UK the voting system is rigged in favour of the two main parties, Labour and Conservative. Votes for other parties are often seen as a wasted vote. Often a voter votes for the Party he dislikes the least. Conservative values as opposed to the parties are somewhat reflected in the Conservative Party, though some would argue it is not so conservative in its values as it once was.

The Labour Party is not just the party for the poor. For instance, it is a much bigger supporter of "abortion rights" than the Conservative Party; the Labour Party would never contemplate reintroducing capital punishment for murder; "progressive politics" has been responsible for weaker and weaker law and order, with shorter and shorter prison sentences to the point where they are nearly useless. In my opinion the Labour Party seems more clueless than the Conservatives on running the finances of a country. And I cannot help but believe that the Labour Party doesn't really care for the poor.. it just uses money to buy votes now, more generously than the Conservative Party and who cares about the long term financial health of the country?

Conservative values verses Progressive values

It is hard to clearly define conservative values to everyone's satisfaction; it is probably even harder to define progressive values.

Progressives believe in intervention in social problems.. i.e. throw money at the problem and it will resolve. The conservative Thomas Sowell argues they almost always fail to think through the overall effects of their proposed interventions. And interventions which are put in place almost invariably overall have the exact opposite effect of the one intended.. the problem gets worse not better.

I would write more, but where to stop? Just listen to Thomas Sowell on Youtube (not Thomas Sewell!!) and you will get some good ideas of the differences between the two political/cultural views.

Not as though I had already attained, either were already perfect: but I follow after, if that I may apprehend that for which also I am apprehended of Christ Jesus.  Brethren, I count not myself to have apprehended: but this one thing I do, forgetting those things which are behind, and reaching forth unto those things which are before, I press toward the mark for the prize of the high calling of God in Christ Jesus. Let us therefore, as many as be perfect, be thus minded: and if in any thing ye be otherwise minded, God shall reveal even this unto you. Nevertheless, whereto we have already attained, let us walk by the same rule, let us mind the same thing. Brethren, be followers together of me, and mark them which walk so as ye have us for an ensample. (For many walk, of whom I have told you often, and now tell you even weeping, that they are the enemies of the cross of Christ: Whose end is destruction, whose God is their belly, and whose glory is in their shame, who mind earthly things.) For our conversation is in heaven; from whence also we look for the Saviour, the Lord Jesus Christ: - Philippians 3:12-20

It is a secular, political viewpoint that a Christian must be of one political affiliation and must not be of another. Our citizenship, that is to say (quite reasonably) our politics are in heaven.

Polis means city and the noun πολιευμα (politeuma), "translated conversation", denotes whatever act can be associated with the verb πολιτευω (politeuo); whatever doings keep the city together, ranging from administration to a good deed: citizenhood.

Therefore our political affiliation is, first and foremost, as subjects of the kingdom of heaven; our citizenship is there. Secondarily, if we have been blessed to live under a government which invites our opinion and participation, we may prayerfully participate in our governments at whatever level and in whatever fashion the Lord leads.

I spent a number of years in a local church wherein the official "teaching" was one of personal choice regarding political affiliation. The atmosphere, however, was one of camaraderie towards conservative Republicans and barely veiled disdain for liberal Democrats. This hypocrisy created a divide within the primary citizenship of the church body. Brothers and sisters, it ought not to be so.

I think a fairly common trap all Christians get sucked into is in thinking that God is on this side or that. That Jesus would be a Republican or a Democrat and endorse their platform wholeheartedly. God, however, is on God's side. You join Him, not the other way around

13 Now when Joshua was near Jericho, he looked up and saw a man standing in front of him with a drawn sword in his hand. Joshua went up to him and asked, “Are you for us or for our enemies?”
14 “Neither,” he replied, “but as commander of the army of the Lord I have now come.”
^{_{Joshua 5:13-14 NIV}}

You'd expect a messenger of God speaking to the leader of God's Chosen People(tm) to respond "I'm totally on your side", but he reminds Joshua that Joshua needs to be on His side. Consider also Jesus in Mark 12

13Later, they sent some of the Pharisees and Herodians to catch Jesus in His words. 14“Teacher,” they said, “we know that You are honest and seek favor from no one. Indeed, You are impartial and teach the way of God in accordance with the truth. Is it lawful to pay taxes to Caesar or not? Should we pay them or not?”

15But Jesus saw through their hypocrisy and said, “Why are you testing Me? Bring Me a denariusc to inspect.” 16So they brought it, and He asked them, “Whose image is this? And whose inscription?”

“Caesar’s,” they answered.

17Then Jesus told them, “Give to Caesar what is Caesar’s, and to God what is God’s.”

And they marveled at Him.

You'll note Jesus gave an apolitical answer instead of the binary one the askers sought. In both cases you have God (or His representatives) attempting to be roped into a political situation and declining to play.

Let me put this into perspective with your question

He told that I contradict myself, calling myself a Conservative and a Christian. He contends that Conservatives show a lack of care for the poor.

Let's back up like Jesus did and look at this a different way. What does he really mean here by "a lack of care for the poor"? Now, not all churches do this well, but few churches are completely ignorant of the poor and many have either direct or corporate support for the poor. I can't say where any of those churches are on the political spectrum, but even the most Liberal or Conservative church will generally not ignore the poor. Even more Christians will personally care for the poor, widows, orphans, etc. without any involvement of their church.

Assuming we're talking American politics, a "Liberal" political position here would mean that most "Christian Conservatives" are opposed to programs that would see the government simply hand out money to the poor. Now, we could debate whether or not this is a "good" policy politically, but the idea that God would squarely land on one side or another is missing the point. God wants the poor cared for. He leaves it to us to make that happen.

Your friend is doing the whole issue a disservice by dismissing the other side of the argument. Is he more interested in helping the poor or winning an argument? That was what the Pharisees and Herodians who came to Jesus missed: taxes are necessary for any government (you should pay your taxes), but they should not hinder the work of God's people either (governments shouldn't overburden people with taxes). They were playing politics and Jesus was playing Church. Don't miss the trees for the forest.

'Conservative' and 'Liberal' are massively over-simplified labels (and which even after over-simplification have different meanings in different places) and asking whether a Christian would fit within one artificially defined camp or another is pointless.

The reality is that people who actually think about politics do not line up exactly with either of those popular labels, and therefore any judgement of a Christian's political position should consider what they actually believe, not what convenient label you have applied to those beliefs.

It's also true that party politics almost always involves compromise. A Christian (or anyone else) who joins a party will always find that they agree with only some of that party's positions. It is up to them to make the judgement whether having to give tacit approval to policies they disagree with is outweighed by the good of promoting something they really agree with.

Saying "lack of care" is far too strong. The difference is not in the degree of care, but in how that care should be provided.

Remember the saying: "Give a Man a Fish, and You Feed Him for a Day. Teach a Man To Fish, and You Feed Him for a Lifetime"?

Liberals notice poverty, attribute it to lack of money, and think that the poor would be better off if they had more money. Conservatives notice poverty, attribute it to lack of meaningful employment, and think that the poor would be better off if they earned more money.

The fish story is relatively recent (at least in that wording), but the idea is far older.

In the 12th century, Mamonides summarized Eight Levels of Charity:

The greatest level, above which there is no greater, is to support a fellow Jew by endowing him with a gift or loan, or entering into a partnership with him, or finding employment for him, in order to strengthen his hand so that he will not need to be dependent upon others

This in turn goes back to biblical principles.

When you reap the harvest of your land, you shall not wholly reap the corners of your field, nor shall you gather the gleanings of your harvest. And you shall not glean your vineyard, nor shall you gather every grape of your vineyard; you shall leave them for the poor and the stranger: I am the LORD your God.
— Leviticus 19:9–10

God doesn't tell the farmers to deliver a percentage of their crop to the poor; he tells them to leave a portion of their crop unharvested, so that the poor can harvest it themselves.

The same principle is expressed in the Christian scriptures:

For you yourselves know how you ought to follow us, for we were not disorderly among you; nor did we eat anyone’s bread free of charge, but worked with labor and toil night and day, that we might not be a burden to any of you, not because we do not have authority, but to make ourselves an example of how you should follow us. For even when we were with you, we commanded you this: If anyone will not work, neither shall he eat.
— 2 Thessalonians 3:7–10

Both liberals and conservatives can be idealists. Liberals think that treating symptoms will alleviate the situation, and feel that the true responsibility of care is up to them. Conservatives think that treating causes will eliminate the problem, and feel that the true responsibility for change is on the recipients themselves.

Both care, but but in different ways.

Notes:

I am not talking about capital-C and capital-L Conservatives and Liberals, but about what in many countries are referred to as small-C and small-L conservatives and liberals.

Many countries have parties that are literally called "Liberal" and "Conservative" (e.g. Canada, UK), but that doesn't necessarily mean that their policies are liberal or conservative, any more than in the US, people opposed to the Democrats want to do away with democracy, or people opposed to the Republicans want to have a monarchy.

The original question didn't name any country, so my answer assumes that it is asking about conservative philosophy, not about any country's Conservative Party's policies. It also assumes the modern American definitions of these two words:

… American conservatism is a broad system of political beliefs in the United States that is characterized by respect for American traditions, support for Judeo-Christian values, economic liberalism, anti-communism and a defense of Western culture. Liberty within the bounds of conformity to conservatism is a core value, with a particular emphasis on strengthening the free market, limiting the size and scope of government and opposition to high taxes and government or labor union encroachment on the entrepreneur. …
— US Conservatism

… in the United States, liberalism has come to include support for reproductive rights for women, including abortion, affirmative action for minority groups historically discriminated against, multilateralism and support for international institutions, support for individual rights over corporate interests, support for universal health care for Americans (with a single-payer option), support for LGBTQ+ rights and marriage equality and opposition to tax cuts for the rich, …
— US Liberalism