WASHINGTON -- Imploring supporters to stick with him, President Barack Obama acknowledged Tuesday that his re-election is not "a slam dunk" because of understandable public skepticism over the economy, but he said his campaign would put forward a vision aligned with the mood of the country.

The president, addressing donors at a hotel near the White House, drew attention to his efforts to heal the economy, end the Iraq war and overhaul health care, but he said "all those things don't mean that much to somebody if they're still out of work right now or their house is still underwater by $100,000. So yeah, this is going to be tough."

Obama said the campaign would pursue "the vision that is truest to our history and most representative of the core decency of the American people."

Obama spoke hours after his top campaign advisers said they were uncertain about which Republican will emerge to challenge him next year, but they predicted a long GOP primary contest that they said will produce a weaker opponent in 2012.

Democrats have been targeting Mitt Romney as the most likely GOP nominee, but noted that Newt Gingrich's surge in the polls has made the Republican contest very unpredictable.

Obama campaign officials noted that only 15 percent of Republican convention delegates will be awarded by the end of February, making it likely that the contest will continue well into the spring.

"They're being tugged to the right every day. I think they're mortgaging themselves for the general by tacking as far as they are," Obama campaign strategist David Axelrod said of the Republican candidates.

He said that would make it more difficult for the nominee "to scramble back" to the center and appeal to a broader base of the electorate for the November general election.