Don S summed up well in one of his posts to the “Republican captivity” post why conservative Christians tend to vote Republican:
I identify with the Republican party more than the Democratic party because it still at least tolerates my values, and at least some office holders and candidates support them. Very few Democratic leaders will stand for absolute right and wrong standards, because they do not want to offend contituents, and they villify me as a “hater” for declaring a sin a sin. They want to grow government to help the poor, but at the same time push any expression of faith from any area of society into which government expands. They use faith to justify the growth of government for this purpose, but deny any individual responsibility to respond to the claims and commandments of Christ, and deny the concept of sin. I am human. If one group of people stands opposed to everything I believe in, and the other group does not, I will stand with that latter group.
Should the Church specifically align with the Republican party? By no means. Can Democrats be Christians? Of course. Will any human government ever achieve heaven on earth or a perfect society? We know the answer to that one. We should never let political involvement distract from our primary purposes of sanctification and evangelism here on Earth. But I don’t think there is a problem with promoting the election of public officials which are more likely to support a governmental environment which will not oppose us in those missions.
One of the other good points that came out of that long conversation is that the mainstream churches (Methodists, Disciples, PCUSA, ELCA, Episcopalians) are definitely in captivity to the Democrats and the whole liberal agenda. (Notice how irrelevant the mainstream liberal churches are, to garner almost no attention through all of this.)
I know many of us conservative Christians used to be Democrats, even liberal Democrats. (I know I was.) Then the party was taken over by 1960′s activists. They ridiculed and demonized our moral conservatism and our pro-life convictions. THAT is what drove us to the Republican party.
We became “Reagan Democrats” and then we shouldered our way into the Republican party. Despite some continued disdain from its country club faction, the party really needed our votes.
If the Republicans become “pro-choice” on the abortion issue, many conservative Christians would abandon that party in a heartbeat. Many would gladly switch to the democratic party if it were pro-life. (I just cannot take seriously all of the Democrats’ rhetoric about helping the poor, the downtrodden, and the little guy, given their stance on abortion.)
But there are other issues that inhibit conservative Christians from the Democratic party. Political liberals today are open to not just political and economic progress, as they used to be, but they also push moral and cultural change. They accept homosexuality, with some even advocating gay marriage. They embrace feminism, even in its most anti-family variety. They tend to be hyper-secular.
In short, conservative Christians were driven out of the Democratic party.