Should candidates for the White House have to pass a religious test? The Constitution says no, but increasingly American political culture says otherwise.

The focus on religion is already evident in the early days of the 2008 presidential race. That’s bad news for the Jews who, for all the talk of “Judeo-Christian” values, don’t meet the religious benchmarks of those who have set themselves up as political judges of a nation they insist is a “Christian” one.

You don’t need to dig very deep to find examples of this partisan piety.

It’s not as prominent on the Democratic side because the party’s liberal base generally draws from faith groups that do not like to make a big production of religion in politics.

Still, most of the Democratic contenders are already working steadily to establish their religious credentials, anticipating faith-based attacks from the Republican nominee in next year’s general election. Sen. Barack Obama (D-Ill.) has frequently invoked his Christianity, and former Sen. John Edwards (D-N.C.) offered a public prayer for the victims of the Virginia Tech massacre “in Christ’s name” — hardly typical talk for a liberal Democrat.

The faith-based politicking is far more intense in the Republican realm, where the evangelical vote will play a key and perhaps decisive role in 2008.

The arbiters of political piety, such as Focus on the Family leader James Dobson, appear willing to judge candidates not just on the issues but on whether they are sufficiently Christian.

That was the case earlier this year when Dobson seemed to dismiss a possible campaign of former Sen. Fred Thompson (R-Tenn.) by telling U.S. News and World Report, “I don’t think he’s a Christian.”

Thompson is a Christian, but some evangelical leaders imply you’re not a real Christian unless you subscribe to their particular version of the religion.

Dobson gave his tacit blessing to former House Speaker Newt Gingrich (R-Ga.), who came on the Focus on the Family radio program, confessed his past adultery and sought Dobson’s absolution. He got it. Dobson, so critical of former President Bill Clinton’s infidelity, apparently had more Christian charity for Gingrich.

You’d think that double standard would turn Dobson into a political liability, but it hasn’t. Republican candidates continue to court him and his fellow Christian right political leaders with a desperation that speaks to their huge influence in American politics.

Sen. John McCain (R-Ariz.), who once described the late Rev. Jerry Falwell as an “agent of intolerance” and said that close ties to religious right leaders were hurting GOP interests, is now fervently courting those same leaders.

Mitt Romney, the former governor of Massachusetts, is finding that even being a conservative doesn’t always help when you’re a Mormon. Last month, evangelical activist Bill Keller told 2.4 million subscribers to his email list that “if you vote for Mitt Romney, you are voting for Satan!”

In 2000, the Anti-Defamation League sharply criticized Sen. Joe Lieberman (I-Conn.), then the Democratic vice presidential nominee, for his frequent references to his religious faith on the campaign trail.

Lieberman, an Orthodox Jew, wasn’t trying to convert anyone or say his religion trumped others. But the ADL rightly argued that when religion becomes just another campaign talking point, it leads to the use of religious tests and benchmarks in the political process.

That, the ADL argued, undermines American democracy and our tradition of religious tolerance. But as the 2008 elections move into high gear, it is evident most politicians have not gotten the memo.