The easy comparison to make about Mitt Romney's candidacy is that of John F. Kennedy. Like Romney, Kennedy was part of a religion that many Americans didn't trust.

Some are calling on Romney to, like Kennedy, make a speech defending his Mormon faith. But will that work in 2012?

David Gibson with the Religion News Service says it's unlkely.

Gibson argues Romney's problem with Republicans isn't his faith, it's his political ideology. Many conservatives just don't trust him.

Romney's biggest task is convincing conservative Christians that he is a conservative, not that he is a Christian. Evangelicals have shown they are happy to back all sorts of unorthodox candidates (anyone remember Herman Cain?). They never fell for fellow evangelicals Michele Bachmann or Rick Perry, and now they are rushing toward Newt Gingrich, a thrice-married convert to Catholicism.

Evangelicals may not love Mormons, but they are really down on moderates. Indeed, Romney is arguably "not Mormon enough," Richard Land, a top Southern Baptist official, said on the eve of the South Carolina vote.

"If his stance on life and his stance on marriage had been consistently what the stance of the Mormon church has been, he would have far less doubts among social conservatives," Land said.

Ralph Reed, head of the Faith and Freedom Coalition and a top evangelical political activist, said he doesn't think Romney's Mormonism will necessarily preclude him from winning evangelical votes or the GOP nomination, so he doesn't need to make the Kennedy speech at this point.

"Bottom line is," said Reed, "he may need to address it as the campaign proceeds, and he may choose to address it as part of a speech down the road."