No one complained when Christine O’Donnell’s admission of high school indiscretions with Hecate became a campaign issue, but Jack Conway’s ad attacking Ron Rand Paul’s undergraduate involvement with a Christian-mocking group at Baylor has struck sober-minded pundits like Chris Matthews and Jonathan Chait and my fellow Beliefnet blogger Rabbi Brad Hirschfield as beyond the pale. Never mind that Factcheck has found the ad’s assertions to be accurate. In America, we frown on religious tests for office, don’t we?

Count me with Conway on this one. Here’s the simple argument. As long as a candidate’s religious identity is just something noted on a bio page–“Baptist” or “Catholic” or “Jewish”–then, sure, leave it alone. But once the candidate puts it into play on his own behalf, it’s fair game. Rand Paul, be it remembered, won the GOP senatorial nomination in Kentucky by convincing James Dobson he was not a soft-on-abortion devotee of atheist libertarian Ayn Rand but a staunchly pro-life Christian. It’s not unreasonable to suspect that the sawdust trail he hit was to the ballot box, not the altar.

There is, in short, no difficulty arguing that if a candidate says, “Vote for me, I’m the Christian,” his opponent is entitled to respond, “Then explain these things.” Unfortunately, in the era of the Christian right Republican candidates are not always transparent about the nature of their religious appeal–using coded language a la George W. Bush and Sarah Palin or sending sly anti-Mormon signals a la Mike Huckabee–all the while maintaining a determined reticence about their actual religious beliefs and commitments.

Democrats have tended to respond by saying, “But we’re religious too.” So because the religion card is being played by everyone, I’d say that if there’s reason to question its face value, let the questioning go on. And if the effect is to discourage politicians from playing the card, so much the better.