score:3
There are many many facts that would account for monogamy :
I might also point out that monogamy was already an established custom in the monarchies that have since become democracies, so the correlation (if any), should only be made between monogamy and monarchies. Since most of the known world was monarchial in nature, this essentially means that we don't have enough data for a correlation.
Upvote:2
Unlikely. Polygamy was banned in Europe centuries before democracy, and it would have been banned for religious reasons rather than men voting to ban it to increase their chances of marriage.