(CNN) -- Rick Warren -- the man at the center of an inaugural firestorm -- has built his career on an uncontroversial reputation.

President-elect Barack Obama has chosen Rick Warren to deliver the invocation at his inauguration.

The irony of the furor over Warren's selection to deliver the invocation at Barack Obama's inaugural ceremony is that the California minister first drew notice for his determination to expand the evangelical agenda beyond hot-button social issues like opposition to same-sex marriage.

Warren has been described as the next Billy Graham, an evangelical leader with a moderate reputation and mass-market appeal -- although instead of massive open-air rallies and an out-sized television presence, Warren focused on forging partnerships with unlikely allies working to protect the environment and fight AIDS.

As a pioneer of the mega-church movement, Warren looked to translate traditional evangelical messages for a wider audience. He penned "The Purpose-Driven Life," a spiritually based self-help guide that brought mainstream best-seller status to a muted religious message.

In his model, everyday concerns were a top priority: Attendees at his Saddleback Church -- now more than 20,000 strong -- could expect free classes on home finance, or assistance with child care needs.

Warren urged ministers to adopt a Madison Avenue approach: to super-charge the growth of congregations by fine-tuning their pitch for the "un-churched." He released bullet-point sermons with crossover potential, along with material to help churchgoers follow along. The church atmosphere he called for was a relaxed one, with dressed-down ministers leading services in nontraditional venues, featuring easy-listening music chosen with younger listeners in mind.

But even as Warren's nonpartisan appeal led to increasingly high-profile roles -- like host of this summer's presidential faith forum, featuring Sens. Obama and John McCain -- controversy grew over his conservative stands on social issues.

The headlines may be new, but Warren's positions aren't. During the last election cycle, he sent thousands of pastors an e-mail laying out what he viewed as non-negotiable issues for evangelicals deciding on their pick at the polls, from stem-cell research and abortion to same-sex marriage.

On Wednesday, after Obama announced Warren as his choice, prominent liberal groups and gay rights proponents criticized the selection. Some said the choice signaled that Obama is not interested in advancing gay rights or protecting abortion rights.  iReport.com: What do you think of the choice?

Joe Solmonese, president of the Human Rights Campaign, said Wednesday that he feels a "deep level of disrespect" because of the choice of Warren and is calling on Obama to reconsider the move. Read more about the criticism of Obama's choice

On Thursday, Obama defended his decision to tap Warren. "And I would note that a couple of years ago, I was invited to Rick Warren's church to speak, despite his awareness that I held views that were entirely contrary to his when it came to gay and lesbian rights, when it came to issues like abortion. ...

"And that dialogue, I think, is part of what my campaign's been all about: That we're not going to agree on every single issue, but what we have to do is to be able to create an atmosphere ... where we can disagree without being disagreeable and then focus on those things that we hold in common as Americans."

But progressive commentators said Warren is a symbol of division.

"When Obama advances a progressive agenda on social issues, as he's certain to do, Warren will continue to speak out on the other side," wrote the Washington Monthly's Steve Benen.

"Only now, he'll do so with the added authority that comes with being the president's hand-chosen pastor for the inauguration's invocation. Warren's status will soar, and his criticism of Obama's policies -- or Democrats' in general -- will resonate that much louder."

Warren himself is working to contain the fallout from his support for California's Proposition 8. In an interview
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