Aug. 15, 2008 -- The presidential campaign has been repeatedly buffeted by religion, and faith will take the spotlight again this weekend as rivals Barack Obama and John McCain make a pilgrimmage to the influential Saddleback Church to woo its best-selling pastor, Rick Warren.
The two candidates will make a joint appearance at the southern California mega-church to be grilled by Warren, the author of "The Purpose Driven Life."
Sen. Obama, D-Ill., will go first, while Sen. McCain, R-Ariz., waits in another room. Each will be questioned for one hour by Warren and asked the exact same questions.
"We're going to look at leadership, specifically their character, their competence, their experience," Warren told ABC News in a interview for "Good Morning America." [WATCH A PART OF THE INTERVIEW HERE]
"I want to give America a better, closer look at the two candidates. I think we want to see not just their values, but their vision, their virtues," he said.
SEE MORE OF ABC NEWS' INTERVIEW WITH RICK WARREN FRIDAY ON "WORLD NEWS TONIGHT WITH CHARLES GIBSON" AT 6:30 PM ET
Warren's blessing could be crucial in the battle for the votes of evangelical Christians, votes that are usually safely Republican. But he has indicated that he won't endorse anyone in the 2008 presidential campaign.
McCain, Obama Seek Evangelical Vote
Warren says he has seen Obama making a play for evangelical voters this year and that Democrats are reaching out to people of faith in ways they havent in recent years.
Obama's bid for evangelical Christians comes as polls indicate a lack of enthusiasm among that community for McCain, who called the Rev. Jerry Falwell "an agent of intolerance" during 2000 campaign but subsequently embraced the conservative religious leader, prior the 2008 campaign.
The powerful and polarizing Falwell passed away in May 2007.
Obama has also been encouraged by an expansion of the evangelical agenda to include poverty, AIDS and the environment.
"Many evangelicals think neither of these guys are evangelical," Warren told "GMA".
He said the key for many evangelicals is the candidates' "relationship to Jesus Christ ... I'm going to give them a chance to explain themselves."
Warren Blasts Edwards for Affair
While McCain has in the past seemed reluctant to talk publicly about his faith, Obama has never shied away from discussing his faith in Christ. The presumptive Democratic nominee has previously visited Saddleback on at least one occasion.
Warren had scathing words for one politician who won't be present this week, ripping into former Sen. John Edwards, D-N.C., for repeatedly lying about having an affair with a woman hired to make videos for his failed presidential campaign.
"There's a difference between forgiveness and trust," he told ABC News. "John Edwards and others like him have lost the trust of America."
The minister said he would have compunctions against voting for someone who cheated on his wife.
"Absolutely I would because if you can't keep your faith to your most sacred vow 'til death do us part, how in the world can I trust you to lead my family? My government?"
ABC News' Teddy Davis reports that the minister who performed the marriage for President George Bush's daughter Jenna cited Warren's comments about Edwards today to rip into McCain, whose first marriage collapsed after what McCain has described as his "selfishness and immaturity."
"His marital history has been duly recorded," said the Rev. Kirbyjon Caldwell in a conference call with reporters. "And as recently as yesterday I think it is, our pastor from Saddleback, Rick Warren indicated that he would not feel comfortable voting for an adulterer and I don't know exactly to whom he was referring but I think the data speaks for itself... At the end of the day again I think the American public deserves full revelation of the candidate's character and competency."
Caldwell also laced into McCain for recently suggesting that his wife enter South Dakota's Buffalo Chips contest, which is a topless beauty pageant.
"My personal opinion and based on my understanding of the Christian faith, that's not not not, N-O-T the type of expression that a presidential candidate, or anyone for that matter who is a follower of the Christian faith ought to make," Caldwell said.
McCain spokesman Brian Rogers said today that the Arizona senator knew that it was a topless contest, but that he was joking and not actually volunteering his wife for it.
Caldwell is part of the Matthew 25 Network, a liberal Christian group, that is going to air a pro-Obama ad on Saturday during the Rick Warren forum.
McCain, who was raised Episcoplian, attending Episcopal High School in Virginia, now attends a Baptist church, and has always appeared ill-at-ease talking about religion.
But his campaign has begun to emphasize his faith.
In an interview with the Chicago Tribune, McCain recalled that while he was a POW during the Vietnam War, he was chosen to be the chaplain to his fellow prisoners and that he relied on his faith to survive.
"I think it's remarkable that I've been able to survive so much and to have the opportunity to do the right thing. I do think we make our own choices, but certainly I think I was meant to serve a cause greater than my self-interest," McCain told the paper.
Obama Knocks Down Muslim Rumors
The battle for the evangelical vote is the latest example of religion affecting the 2008 race for the White House.
Obama has had to deal with persistent rumors that he is Muslim, an accusation that he tried to parry early on with the quip, "This would surprise my pastor at Trinity United Church of Christ.
But Obama had to eventually leave the church because of the fiery sermons by his pastor, the Rev. Jeremiah Wright, who was quoted in the wake of 9/11 saying the United States had provoked the attack and railed, "Goddamn America."
McCain was forced to reject the endorsement of two ministers.
The Rev. Rod Parsley's backing was rejected after he made disparaging remarks about Islam, and Pastor John Hagee's blessing was rebuffed for making controversial comments about the Holocaust and Catholics.
During the Republican primary, former Massachussets governor Mitt Romney's Mormon faith was an issue for many in the conservative GOP base as some Christian leaders denied that Mormonism was a Christian religion.
Another GOP contender was former Arkansas governor Mike Huckabee, a former minister who had to deny that his December commercial intentionally included a cross-shaped glint of light in the background, in a sly appeal to evangelicals.