"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, and now a politics professor at the University of Southern California. 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 that were eliminated when Bain Capital, a takeover firm that 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 any incumbent.
Yet 78 percent said he's a likeable person, which forces Republicans to be careful. It's possible Obama will run a more cut-throat campaign than will his challenger. For now, anyway, Romney calls Obama "is a nice guy" who doesn't know how to lead.
Republican 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 one-fourth of the support in Republican polls. Rep. Michele Bachmann of Minnesota emerged as his main challenger last summer, only to be supplanted by Perry. A few halting debate performances hurt Perry, and former pizza company executive Herman Cain replaced him at or near the top of the polls, along with Romney.
Last week, Cain tried to swat down allegations of sex harassment from the 1990s. Party activists are waiting for the impact. Some, however, think Cain's lack of political experience and his unorthodox style, which includes largely ignoring Iowa and New Hampshire, are more likely to bring him down.
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 longshots such as Bachmann and Cain. Republicans have a history of nominating the runner-up from previous primaries, and Romney fits that bill.
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 never placate conservative voters because of his establishment ties and the more liberal positions he once held on abortion, gay rights and gun control.
If this view is right, the shifting support for Bachmann, Perry and Cain is more than a flirtation, and someone will emerge as the "non-Romney" who wins the nomination.
Veterans of past presidential campaigns tend to doubt this outcome. But even with Obama's economic woes, plenty of Republican insiders worry that Romney's inconsistency on important issues and voters' doubts about his authenticity could let the president slip away.
Romney should have put his GOP rivals "in the rear-view mirror" by now, said Mike McKenna, a Republican lobbyist who has tracked focus groups and polls in various states. "The problem is, a huge part of the party views him as a third Bush term."
McKenna said pundits don't realize that the tea party movement was as much a rejection of the high-spending, high-deficit practices of President George W. Bush and Republican lawmakers as it was a reaction against Obama's health care plan. With his ties to New England and the party establishment, Romney "looks like the lineal descendant of Bush," McKenna said.
He said he fears that a lot of conservatives will sit out the 2012 election if Romney is the nominee.
Plenty of strategists reject that view. They think conservatives' deep antipathy toward Obama will cause them to overcome their misgivings and fully back Romney.
David Axelrod, Obama's top political adviser, points to issues Obama can cite success on, from health care and undermining al-Qaida to reviving the auto industry and ending the Iraq war.
"We're going to have a very robust debate," he said. "The Republicans say if we just cut taxes and spending and regulations, we will grow. And I think the American people understand it's more complicated than that."
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