But the race's contours are starting to come into view.
It's likely that the campaign will be a close, grinding affair, markedly different from the 2008 race. It will play out amid widespread economic anxiety and heightened public resentment of government and politicians.
Americans who were drawn to the drama of Obama's barrier-breaking battle with Hillary Rodham Clinton, and the up-and-down fortunes of Sen. John McCain and Sarah Palin, are likely to see a more partisan contest this time, with Ohio and Florida playing crucial roles, as they did in 2000 and 2004.
Republicans have their script, and they just need to pick the person to deliver it: Portray Obama as a failed leader who backs away from challenges and doesn't understand what it takes to create jobs and spur business investment.
Obama will highlight his opponent's ties to the tea party and its priorities. He will say Republicans are obsessed with protecting millionaires' tax cuts while the federal debt soars and working people struggle.
On several issues, voters will see a more distinct contrast among nominees than in 2008. Even the most moderate Republican candidates have staked out more rigidly conservative views on immigration, taxes and spending than did McCain.
Democrats say Obama has little control over the two biggest hurdles to his re-election: unemployment and congressional gridlock. The jobless rate will stand at levels that have not led to a president's re-election since the Great Depression. Largely because of that, Obama will run a much more negative campaign, his aides acknowledge, even if it threatens to demoralize some supporters who were inspired by his 2008 message of hope.
The tea party, one of the modern era's most intriguing and effective political movements, will play its first role in a presidential race. After helping Republicans win huge victories in last year's congressional elections, activists may push the GOP presidential contenders so far right that the eventual nominee will struggle to appeal to independents.
"It's going to be extremely different, with much more hand-to-hand combat, from one foxhole to another, targeted to key states," said Chris Lehane, who helped run Democrat Al Gore's 2000 presidential campaign.
Republican consultant Terry Holt agreed. "You can expect a very negative campaign," he said. "In 2008, Barack Obama was peddling hope and change. Now he's peddling fear and poverty." Obama and his aides reject that characterization, of course.
They say the Republican candidates are under the tea party's spell, noting that all of them said they would reject a deficit-reduction plan even if it included $10 in spending cuts for every dollar in new taxes.
Both parties agree that jobs will be the main issue. The White House predicts unemployment will hover around 9 percent for at least a year, a frighteningly high level for a president seeking a second term.
GOP lawmakers, who control the House and have filibuster power in the Senate, have blocked Obama's job proposals, mainly because they would raise taxes on the wealthy. The candidates, echoing their Republican colleagues in Congress, say new jobs will follow cuts in taxes, regulation and federal spending.
With the economy struggling and Obama hemmed in legislatively, his advisers sometimes say the election will be a choice between the president and his challenger, rather than a referendum on the administration's performance.
"That's a very genteel way of saying 'We're going to rip your face off,' " said Dan Schnur, a former aide to McCain and other Republicans. Obama has little choice but to try to portray the GOP alternative as worse than his own disappointing record, Schnur said.
Some Republican candidates would be tougher targets than others. Texas Gov. Rick Perry promotes his state's significant job growth, leaving Democrats to grouse that he was a lucky bystander rather than the cause.
Former Massachusetts Gov. Mitt Romney says his years in the private sector make him best suited to lead an economic expansion. But Obama's allies have gathered details of jobs eliminated when Bain Capital, a takeover firm Romney headed, restructured several companies.
Obama can't fine-tune his strategy until Republicans pick their nominee, and that may take months. So he's spending part of this year traveling to some of the most contested states, telling disappointed liberals he still deserves their strong backing and trying to convince centrists that he can revive the economy.
Obama's overall job-approval rating was 46 percent in an Associated Press-GfK poll from October. Only 36 percent of adults approved of his handling of the economy, a worrisome number for an incumbent. Yet 78 percent said he's a likable person, forcing Republicans to be careful.
GOP insiders see Romney as their most plausible nominee. He has run the steadiest and best-financed campaign thus far, relying on lessons and friends picked up in his 2008 bid.
But the GOP race has been unpredictable, and Romney has struggled to exceed a quarter of the support in Republican polls.
Two schools of thought run through Republican circles. One holds that Romney is the logical nominee and will consolidate the party's somewhat grudging support after conservatives stop flirting with long shots such as Rep. Michele Bachmann and businessman Herman Cain.
The competing theory holds that Americans are angrier at government and the two parties than political pros realize, and the tea party is just the start of a potent, long-lasting movement. Under this scenario, Romney can't placate conservatives because of his establishment ties and his formerly more liberal positions on abortion, gay rights and gun control.