WASHINGTON -- When Mitt Romney's father ran for the presidency 40 years ago, his Mormonism was not an issue. When Mo Udall was a major challenger for the Democratic nomination in 1976, his religion was so irrelevant that today most people don't even remember that Udall was a Mormon.

Five members of the Senate are Mormon. Are there any intimations that the Mormonism of Harry Reid, Orrin Hatch, Gordon Smith, Michael Crapo or Robert Bennett corrupts, distorts or in any way diminishes their ability to perform their constitutional duties?

Mormonism should be a total irrelevancy in any political campaign. It is not. Which is why Mitt Romney had to deliver his JFK "religion speech" this week. He didn't want to. But he figured that he had to. Why? Because he's being overtaken in Iowa. Why Iowa? Because about 40 percent of the Republican caucus voters in 2000 were self-described "Christian conservatives" -- twice the number of those in New Hampshire, for example -- and, for many of them, Mormonism is a Christian heresy.

That didn't seem to matter for much of this year when Romney had a commanding lead and his religion seemed a manageable political problem -- until Mike Huckabee came along and caught up to Romney in the Iowa polls.

The appealing aspects of Huckabee's politics and persona account for much of this. But part of his rise in Iowa is attributable to something rather less appealing: playing the religion card. The other major candidates -- John McCain, Rudy Giuliani and Fred Thompson -- either never figured out how to use it or had the decency to refuse to deploy it.

Huckabee has exploited Romney's Mormonism with an egregious subtlety. Huckabee is running a very effective ad in Iowa about religion. "Faith doesn't just influence me," he says on camera, "it really defines me." The ad then hails him as a "Christian leader."

Forget the implications of the idea that being a "Christian leader" is some special qualification for the presidency of a country whose Constitution (Article VI) explicitly rejects any religious test for office.

Just imagine that Huckabee were running one-on-one in Iowa against Joe Lieberman. (It's a thought experiment. Stay with me.) If he had run the same ad in those circumstances, it would have raised an outcry. The subtext -- who's the Christian in this race? -- would have been too obvious to ignore, the appeal to bigotry too clear.

Well, Huckabee is running against Romney (the other GOP candidates are non-factors in Iowa) and he knows that many Christian conservatives, particularly those who have an affinity with Huckabee's highly paraded evangelical Christianity, consider Romney's faith a decidedly non-Christian cult. Continued...