On the presidential campaign trail, John McCain shies away from pious prose. He is a man for whom the terms "public declaration" and "faith" do not go together, the product of an Episcopalian upbringing who treats religion as a private matter.

Yet McCain identifies himself as a Southern Baptist. And he is not averse to invoking that label when stumping in the Bible Belt.

So why hasn't the 72-year-old Republican taken the Baptist plunge? Why after attending the North Phoenix Baptist Church for more than 15 years has he yet to be baptized by immersion?

For some Christians, McCain's disclosure last spring that his wife, Cindy, had been baptized but he had not raised questions about the candidate's sincerity. But it was in keeping with McCain's circuitous journey of faith—a path that has become something of an obstacle course for wooing the religious conservatives who are an important part of the Republican base.

For one thing, McCain's support for embryonic stem cell research troubles some conservative Christians. They fear that the foundation of his stance against abortion could shift as well. Others question his use of the Baptist label, arguing that by avoiding baptism he has avoided the most sincere public declaration of the Baptist faith.

And then there is the acerbic tone McCain sometimes uses in speaking of religious faith.

"It's a problem for him in many ways," said Jim Guth, a political science professor at Furman University in South Carolina who has studied religion and American politics for nearly 30 years.

"Mr. McCain seems to be sort of tone-deaf to evangelical language," Guth said. "One would think he would have a better understanding of that tradition. He very consistently doesn't seem to have an ear for the kind of rhetoric that someone appealing for an evangelical constituency would use."

Sometimes McCain's silence and sarcasm are taken as insensitivity.

A McCain Web ad featured Obama as a self-proclaimed messiah. Obama supporters called it an attack ad that equated Obama with the Antichrist. In an interview with the Tribune, McCain scoffed at critics of that ad, suggesting they "relax, enjoy life and have a sense of humor."

Perhaps that was his thought when a journalist covering the 2000 campaign asked McCain to recall his favorite Bible verse. When the senator came up with nothing, the reporter suggested John 3:16—"For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life." This oft-quoted verse in the New Testament has been called the "Gospel in the nutshell."

"Is that the one about the end of the world?" McCain quipped.

Guth said evangelical Christians would be hard-pressed to find that funny.

Richard Land, president of the Southern Baptist Convention's Ethics & Religious Liberty Commission, said if he advised McCain—and he hasn't—he would tell him to stay "in his comfort zone." Anything else will sound contrived and calculated. He also said McCain's faith doesn't matter as long as he remains a steadfast foe of abortion.

But Randall Balmer, author of "God in the White House," contends that McCain's comfort zone might be hard to define, given the Arizona senator's struggle to define his own faith. Though McCain calls North Phoenix Baptist his spiritual home, his profiles in political almanacs, regularly updated by his press office, continue to list him as an Episcopalian.

Referring to baptism by immersion in a recent interview, McCain said, "Oh, it's just something I'll be able to work out with Pastor [Dan] Yeary," referring to his minister.

Balmer said that "to be unsure of his own religious moorings makes it difficult to make a persuasive case."

"I suspect it's a dual identity."

But there is no such thing as a dual identity when it comes to being a Baptist. You either are or you aren't. And without immersing yourself in baptismal waters, you should not claim to be, Balmer said.