John McCain and Barack Obama bickered for weeks over the kind of debates they wanted -- but when California pastor Rick Warren asked them to put that aside and join him for a candidates' forum, the answer, of course, was yes.

The two political rivals will join Warren Saturday evening at his 23,000-member Saddleback Church, taking the same stage to answer the same questions for the first time.

The event is not technically a debate, or the kind of free-form joint town hall meeting McCain had advocated. Warren will ask each candidate the same set of questions separately.

But the mega-church leader's ability to bring the candidates together is a testament to his clout and reputation as a centrist leader of a new evangelical agenda.

Watch the forum live on FOX News starting at 8 p.m. ET Saturday.

Warren is an anti-abortion Southern Baptist, yet he is part of a movement to shift the Christian right's focus away from abortion and gay marriage. He turns instead to poverty, disease, illiteracy and other challenges around the world.

His forum Saturday will no doubt elevate his already prominent role at the intersection of religion and public life.

"What I'm trying to do is stake out what I call the common ground for the common good," Warren told FOX News on Friday, saying Americans are "disaffected" by both the secular left and the religious right.

"I'm neither of those," Warren said.

"Rick Warren is really the anti-Jerry Falwell," said Alan Wolfe, director of the Boisi Center for Religion and American Public Life at Boston College.

Wolfe told FOXNews.com that Warren has the ability to broaden the evangelical agenda, but he said Warren's clout stems from a "movement on the ground."

"He's giving them a voice, and it's very important," he said. "I think he's a major figure, definitely America's next Billy Graham."

Warren, author of the best-selling book "The Purpose-Driven Life," has with his wife, Kay, been a leading advocate for HIV/AIDS victims worldwide.

That folds into his ambitious global project, called the PEACE Plan, which sends local church members on humanitarian missions abroad, where they link with members of others local churches, businesses and governments.

The program has drawn attention for its work in Rwanda, but PEACE Plan director Mark Affleck said nearly 8,000 Saddleback members have traveled to 68 countries since the program first launched in 2003.

Warren's vision, which he hopes will be replicated around the globe, addresses not just spiritual needs but practical ones. It puts less emphasis on aid organizations or grants and more on the faith and deeds of individual Christians.

And the presidential candidates are eager to associate themselves with this pastor of international acclaim.

"Neither can be harmed by this. Both will benefit from this," Wolfe said, adding that Obama will probably benefit more because it's a "given" that Republicans are associated with evangelical churches.

But it is McCain who has been seen as struggling talking about his religious faith, even though his views fall more in line with those of evangelicals.

Unlike many Democrats, Obama has proved comfortable talking about his Christian faith publicly.

The campaign has been diligently courting religious voters with a presence on Christian radio and blogs and through "American Values Forums" and other events.

Hot-button campaign issues are expected to be off the table Saturday -- instead Warren will touch on his broader priorities.

Warren representative A. Larry Ross said the forum will cycle through four areas: stewardship, leadership, worldview and America's role in the world.

"Pastor Rick feels that a lot of these debates produce more heat than light, and he wanted to give the candidates the opportunity for more long-form answers," Ross said.

Each candidate will have about 50 minutes with Warren. Obama will go first, and McCain will not be allowed to hear the questions that are being asked. The two candidates will then meet briefly on stage for a handshake and photo op before McCain takes his turn.

Warren does not endorse presidential candidates. Though he has faced some pressure from older-guard evangelicals who oppose broadening their agenda, Warren remains unfazed.

"When you try to do a middle ground, you've got enemies on both sides," Warren said.

And while evangelicals overwhelmingly supported President Bush in the last two elections, Warren said neither candidate can take that vote for granted.

"I don't know what's going to happen with the evangelical vote. Nobody's ever predicted it correctly and I certainly wouldn't try to do that," he said. "It's always been misunderstood to be a monolith -- it isn't."

FOX News' Judson Berger and Anita Vogel and The Associated Press contributed to this report.