Conservative Christians used to be all over the map politically, with probably more of them in the Democratic camp. What happened? Why are they now tending towards small government political conservatism? I think Michael Gerson, in the context of a column on another issue, hits it exactly:
Among conservative Christians, government is often viewed as a force of secularization — a source of both bureaucratic regulation and moral deregulation.
Government, including liberal governments as in those who followed the New Deal, left religion and traditional morality alone. Then the government outlawed prayer in public schools, legalized abortion, scrubbed the public square of religious references, says that homosexuality is OK, etc., etc. Christians started seeing their government, as Gerson says, as a force for taking religion out of consideration and for promoting secularism.
I’m not saying that some of those changes might not have been necessary. I’m just saying that this is why so many Christians are now alienated from their government.