Rick Warren is an influential pastor, and that influence extended pretty directly to politics when he hosted a forum at which both Barack Obama and John McCain appeared during the 2008 campaign for separate, one-on-one conversations with Warren at his Saddleback Church. Some of Warren's comments about homosexuality led to a mini-firestorm of controversy before the forum--and again when Obama asked him to give the invocation at his inauguration--but Wendy Kaminer notes how Warren is sticking by his apolitical guns, most recently at an event hosted by the Pew Forum in DC last month.
Kaminer has some questions about the legitimacy of claiming disinterest in politically charged government policy when it directly relates to one's stated interests (as health care would seem to for Warren), but Warren serves an important political function in the present day, and he will probably continue to do so in 2012: in his apolitical identity, he is a link for President Obama to religious, socially conservative voters--a pathway for interaction, albeit on Warren's less-than-political terms (discussion at his '08 forum focused as much on macro, introspective topics of personal belief as on anything political).
There is a solid movement of liberal/progressive Christian groups in America today, built ideologically on New Testament altruism and the seemingly-liberal-minded, help-the-sick, feed-the-masses side of Christian values and Christ's story and identity. (Note: That's a description of the political ideology and religious interpretation behind Christianity-driven liberalism--not intended as a statement about Jesus. Given that we have four different stories about Jesus' life set down in the Bible, identifying his politics makes for a fun and controversial game--one best played outside the Politics Channel.) Not that helping the sick is necessarily liberal-minded: Bush's compassionate conservatism brought us an expansion of global AIDS funding, though with some social conservatism built in.
Rick Warren seeks to encapsulate that shared altruistic feeling, but without the trappings of liberal or conservative politics. Given his comments on gays, it's not hard to tell where his social affiliations lie, and perhaps this is an unfair judgment about his followers, but I'd bet that he's more of a portal, for someone like Obama or McCain, into the pool of conservative Christians in American than he is into the pool of liberal ones.
Now that the political ascendancy of the religious right has faded, somewhat, in American politics with the GOP's defeat in '08 and the rise of fiscal conservatism in '09, the opportunity to present oneself as a religiously conscious individual is a valuable thing for a Democratic presidential candidate, or as an incumbent Democratic president seeking office again--because without the reigning influence of Evangelical conservatism, more religiously minded votes might be up for grabs.
The relationship with Warren is a significant one for President Obama--one that is necessarily tenuous, given the tension between Warren's views and the views of Obama's LGBT-rights-supporting base. But Warren remains a political player, despite and because of his lack of politics: who else can host both the Republican and Democratic presidential nominees onstage, and hold that discussion in a politically neutral environment?
It wouldn't be surprising to see Warren in that same role again in 2012--as a politically neutral go-between for presidential candidates desiring a place to talk about religious values during the heat of a campaign. Remaining apolitical is a big part of that position in which Warren now finds himself, post-2008.