score:12
As far as I know this has never happened. I believe that this is because it is a really tough clause to do anything with:
To start with, it would typically take massive disenfranchis*m*nt (100k voters+) to cost a state a representative in Congress. (Sure, it's possible that a state is right on the edge and a handful of voters would make a difference, but it's pretty unlikely, and in nearly all cases of disenfranchis*m*nt, it won't be close.) The law works very much on a "no harm no foul" basis and the courts would not consider a case which made no material difference. Nor would Congress.
A law which makes it hard to vote is not the same as a law which denies the right to vote and it's only the latter which is prohibited here. When the Constitution uses categorical terms the courts -- correctly -- are loath to substitute their own judgment of what ought to be. It would be hard to get a Federal court to take such a case and it would not be easy to argue in Congress than the clause had been violated.
Historically, Congress is the judge of such things and has always viewed getting too deeply into judging individual states' electoral matters as a Can of Worms. And politicians don't like cans of worms. They tend to reserve such things to cases which (1) are really egregious or (2) benefit their own party (and preferably both!)
I think that if Congress were to take action, it would require a vote by both House and Senate, so in the first hundred years (when the South was solidly Democratic) the only time such a decision could have passed is when the Republicans had a big majority in both houses. (I say a "big majority" because I suspect that there would be moderates who would be uncomfortable with such an obviously partisan move.) This didn't happen often.
Finally, it would be a tough case for an individual to prosecute since the US court system does not allow theoretical suits. To file, the person filing the suit must have been personally harmed and it would be difficult to establish that you have been personally harmed by your own state failing to lose representation in Congress. Inhabitants of whatever state would have picked up a seat arguably would be harmed, but the courts usually say that such harms are too indirect to provide standing. (One state could sue another, but this is very rare and only the state that stood to gain a seat would have standing.)
Note that what the country eventually did do was pass the Voting Rights Bill which rather invasively regulated voting in many states where there was de facto denial of the opportunity to vote and because it dealt with de facto rather than de jure denials, was probably more effective.
Upvote:23
Some legal scholars argue that section 2 was essentially revoked by the 15th Amendment, only a year and a half later.
Section 2 basically says, "If you insist on discriminating in voting rights, here's what's going to happen to you", whereas the 15th amendment flat out prohibits racial discrimination in voting rights.
There have been multiple cases that referenced section 2, but always at its margins (usually in relation to its criminal exemption). Hunter vs. Underwood is interesting, as a state tried to use section 2 to enable voting discrimination by employing a racist criminal statute.
It does seem that Congress made an attempt to invoke Section 2 after the census of 1870, but "was unable to identify enough disenfranchised voters to make a difference to any state's representation." There was also a lawsuit in 1945 against the Virginia poll tax that tried to employ it, but it got dismissed.