Saddleback Church is the nation's largest church. Its senior pastor, Rick Warren, is bigger still. His best-selling book, "The Purpose-Driven Life," is the sentinel of an evangelical movement designed to do nothing less than bring about a second Reformation in world Christianity. In the millions of lives he has touched, the 350,000 pastors he has trained, the global network he is creating, and the serious acts of charity he performs, Warren is charting the future of 21st-century religion.

He also may be influencing the future of American politics, and that's where a few questions arise.

I met Warren recently at a small, on-the-record conference of journalists sponsored by the Pew Forum on Religion & Public Life. He's a charming, utterly likeable guy, with a hearty and generous laugh, a manner so casual he wears a suit only once a year — on Mother's Day, to honor his wife.

Warren's mission is divine and defined, and boy, is he ever good at it.

Twenty-five years ago, newly ordained, he moved to Orange County with his wife and child and set about starting a church. He went door to door, surveying anyone who was estranged from religion to find out what drove them away. It wasn't theology, he discovered. It was style.

So he created a church for people who hate church, a warm and inviting antidote that would grow large enough to need 30 acres of parking but would retain a personal character through small study groups that now number in the thousands.

"I'm addicted to changing lives," Warren says. "I'm a simplifier and a synthesizer."

Indeed, the message in his books, CDs and online sermons is simple: Putting God in the center of your life gives you hope and purpose, and, through Jesus Christ, the only chance at eternal life. It is an upbeat, nonpolitical, post-denominational message that is light on theology but bursting with possibilities for feeling good by doing good.

Warren has extended his influence by teaching pastors to lead their own congregations in his "40 Days of Purpose" program. And by virtue of a winning personality and clever public relations, he's extended his influence further into celebritydom, talking with rocker Bono about AIDS prevention in Africa, pontificating on Sunday talk shows, signing books to heads of state (including, improbably, Fidel Castro).

The success of Saddleback and churches like it poses a direct, immediate challenge to mainstream Christianity. Warren says that 78 percent of his members had no religious background; clearly, his brand of evangelicalism is addressing spiritual, psychological and sociological needs that conventional churches have left wanting.

But as his celebrity grows, Warren also may be challenging mainstream politics. He wears his socially conservative political agenda as comfortably as a Hawaiian shirt.

"I'm not a politician, I'm a pastor," he asserted, and then noted that if evangelical Protestants teamed up with American Catholics, "that's called a majority."

He distances himself from the strident, narrow agenda of traditional evangelical leaders — especially in his noble work combating poverty and disease. But it's hard to tell whether he realizes how much power he could have.

At the conference, he followed a reasonable biblical argument against gay marriage with an offhand comment comparing homosexuality with something that I won't dignify by repeating. He tried to convince Jews that they could still be Jews if they accepted Jesus Christ, and he implied that little separated Catholics and evangelicals — when their actual theological differences are profound.

It remains to be seen how religious and other minorities would fare in the purpose-driven world Rick Warren envisions. He believes he is doing God's work. But God only knows if that's so.