President Obama faces a wide-open Republican field of challengers in 2012, one of his top advisers said.

David Axelrod, the senior aide who just stepped down from his official position at the White House, said the GOP race for the presidential nomination is the "most unpredictable" he's ever seen.


"This is the most unpredictable, unfathomable nominating process on the Republican side in my lifetime," Axelrod told USA Today in one of his many outgoing interviews.

Axelrod noted the tendency of Republican voters to opt for a candidate who's run before, or waited patiently for an opportunity to run for president. But the departing adviser, who's expected to play an integral role in the president's reelection campaign, said it seems no candidate who fits that mold.

"Generally, the Republican Party has been pretty predictable — it's been a hierarchical party; the elders of the party get together that someone who's sort of been in the queue will have their turn," he said. "There is no such pecking order this year, and there's no process to impose a sort of top-down nomination process. So I don't know who the nominee is, and I suspect that if you talk to leading Republicans, they don't know either."

Polls of Republican primary voters have shown that former Massachusetts Gov. Mitt Romney, former Arkansas Gov. Mike Huckabee and former Alaska Gov. Sarah Palin are ahead of the pack in the race for the Republican nomination. All three played a role in the 2008 campaign — Romney and Huckabee as candidates for president, Palin as the vice presidential nominee — though none has jumped out to a commanding lead in the 2012 campaign.

Other candidates considering a run are working to make names for themselves in states like Iowa, New Hampshire or South Carolina, which host the first three nominating contests of the 2012 cycle.

One new name in the mix has been U.S. Ambassador to China Jon Huntsman, a former Republican governor of Utah. ABC News reported Monday that Huntsman is expected to resign his job in the Obama administration to consider a run against his boss, the incumbent president.