One day, in a sardonic jibe at some conservative who was piously claiming the mantle of heaven, I told my wife, "Don't forget, God's a Republican." Without missing a beat, she replied, "But his son's a Democrat."

Between the Old Testament Jehovah and the New Testament Jesus, a Christian can find support for almost any ideological perspective. American religion used to have room for many different political views, and American politics used to feature religious people across the entire ideological spectrum.

At one time, mainstream denominations were just as likely to tilt to the left as to the right. Back during the 1960s, as a teenage Christian conservative, I was continually annoyed by antiwar ministers and priests who admired Che Guevara.

At the height of the Cold War, U.S. Catholic bishops called for nuclear disarmament. In 1983, I went to a Lutheran service expecting a sermon commemorating the 500th anniversary of the birth of Martin Luther.

Instead, I heard a denunciation of President Ronald Reagan's policy in El Salvador.

Experiences like that drove me from church to church in search of a nonpolitical version of Protestantism. They eventually also helped drive me from religion entirely. Today, something similar is happening, but the push is coming from the right, not the left.

It may have started in 1979, when Southern Baptist minister Jerry Falwell founded the Moral Majority to mobilize evangelicals behind conservative political causes. Reagan and other Republican leaders were more than happy to make use of religious sentiments to attract votes.

It looked like a perfect match: Evangelicals gained political influence, and the GOP acquired a loyal bloc of supporters.

But today, it looks increasingly like a bad bargain that dramatizes the risks of interweaving politics and religion. As these believers became more vocal and visible in the Republican Party, they sent an unmistakable message: If you're not a conservative, you're not a Christian.

So a lot of people who are not conservative but once would have gone to worship services have decided they don't belong. They see the GOP claiming to represent the will of God and run the other way.

"Each year, fewer and fewer Americans identify as secular Republicans or religious Democrats," write political scientists David E. Campbell and Robert D. Putnam in the current issue of Foreign Affairs. "Formerly religious Democrats (except among African Americans) have drifted away from church, and formerly unobservant Republicans have found religion."

That may sound like a reasonable trade for conservative Christians. Who needs skeptics and scoffers anyway? But it has some side effects they may come to regret.

One is that they are losing leverage and consideration in one of the two major parties. President Barack Obama's proposal to make religiously affiliated universities and hospitals provide contraceptive coverage to employees might not have occurred if religious folk were more numerous in the Democratic ranks.

Another consequence is that making the Almighty synonymous with political conservatism breeds contempt for faith. Young people now are far more likely alienated from religion than their forebears were. In the 1970s, only 12 percent of people in their 20s disavowed any religious affiliation. Today, 33 percent do.

The change has a lot to do with the fact that "millenials" tend to be liberal or libertarian on social issues. When they hear Republicans invoking the Bible to justify banning same-sex marriage, many deduce that Republicans are too intolerant to bear—and so is the Bible.

The people with no religious affiliation lean strongly Democratic. In 2008, 75 percent voted for Obama, compared to 45 percent of Protestants and 54 percent of Catholics. Even in 2010, a Republican year, 68 percent of them voted Democratic for Congress.

The Republican practice of spurning "none/other" voters (basically, all who don't identify themselves as Christians) could turn out to be a fatal error. The Georgetown University blog Nineteen Sixty-four says they are now so numerous that "Obama could lose both the Catholic and Protestant vote to the Republican nominee—even lose badly—and still win re-election."

As the nonreligious proliferate, the GOP may find it has foreclosed any chance of winning their votes. What it hears from this group comes straight from the old country song: "God may forgive you, but I won't. Yes, Jesus loves you, but I don't. They don't have to live with you, and neither do I."