"In 2008 it was an open seat and it attracted a lot of candidates on both sides," said Cal Jillson, a Southern Methodist University political scientist. "Now we have a case with an incumbent Democratic president who appeared a few months ago to be highly vulnerable -- but since then has gained a lot of momentum."
The Democratic Party is not likely to produce a significant primary challenge for Obama. But the Republicans -- including many repeats from 2008 -- are expected to field up to 15 candidates. So where are they?
So far, none of the expected front-runners has formally declared their intention to run. Even Obama has yet to file papers.
"If you ever see me sign up for a gig on Fox News, it'll be a clear indication that I've decided to run for president," former Massachusetts Gov. Mitt Romney told Jay Leno recently on the "Tonight Show." Three of the top prospects have regular slots on Fox.
Mike Huckabee, former governor of Arkansas with his own show on the network, had a strong start in the early states in 2008, only to experience a slow fade as the primaries wore on.
"Very few people can sustain the burn rate of a campaign if it's going to have to last 18 months," Huckabee said recently on Fox. "You can't raise and go through that much money."
Despite his name recognition and national television platform, Huckabee finished far behind the pack in last week's New Hampshire Republican straw poll -- an early, some might say premature, indicator of that state's primary voter interest.
Romney led the straw poll with 35 percent, while Rep. Ron Paul of Texas finished second with 11 percent. Former Minnesota Gov. Tim Pawlenty had 8 percent and former Alaska Gov. Sarah Palin finished with 7 percent.
Former House Speaker Newt Gingrich, Indiana Gov. Mitch Daniels and Huckabee each finished with 3 percent. Former New York Mayor Rudolph Giuliani and developer Donald Trump got 1 percent each.
In interviews, the prospective candidates have cited the length and expense of campaigning as reasons for their delay, along with the risk of overexposure, the danger of peaking too early, and more.
Other possible contenders include Rep. Paul Ryan of Wisconsin, former Pennsylvania Sen. Rick Santorum, Mississippi Gov. Haley Barbour, and Sen. John Thune of South Dakota, who recently told a local television station that he is still making up his mind.
"I'm going to have to make a final decision here in the not-too-distant future," Thune told KELO- TV. "If you're going to be a candidate, you pretty much have to be getting out there, particularly for somebody like me who's not known. A lot of the candidates are well known."