A dramatic new consensus has taken hold inside the campaigns of President Obama and Mitt Romney, one that was unthinkable just a few weeks ago: Americans will wake up on Election Day not knowing who their next president will be.

Polls have tightened, with trend lines in several key states favoring Romney, and Monday's foreign policy debate in Florida doing little to radically alter the shape of the race.

Romney spent much of the year working to shore up his conservative flank. But now, buoyed by his vigorous first debate performance, he plans to spend the remainder of the campaign visiting swing precincts where both campaigns are competing for a diminishing slice of undecided or persuadable suburban women.

Obama campaign officials now privately acknowledge that North Carolina, a state they can afford to lose, is moving perilously out of reach. Internal polling shows Florida also moving slightly toward Romney, but few in either camp believe the Republican nominee has more than a 1- or 2-percentage-point edge here.

Both campaigns consider Virginia and Colorado tight, with Romney perhaps hanging on to a tiny shred of a lead.

New Hampshire is now a jump ball, and the Romney campaign is making a last-minute investment on expensive Boston area television ads in an attempt to turn the state red.

The president's re-election chances increasingly hinge on a "Big Ten" firewall of Iowa, Wisconsin and, most importantly, Ohio -- a state where Romney has been stymied by his opposition to the federal auto bailout and a concentrated effort by Obama forces to portray the former private equity whiz as out of touch with the middle class.

The Obama campaign is highlighting polls showing robust leads in early voting and absentee balloting in Iowa and Ohio, but Republicans have worked to close the wide early voting gap that helped drive Obama's victory in 2008.

Still, both campaigns are seeing the race narrow in those Midwestern states, which just weeks ago were thought to be firmly in Obama's grasp.

Even some Democrats admit that, for the moment, the momentum is on Romney's side.

"What is holding the president back is voters still don't know what he is going to do early next year to get this economy going," Democratic pollster Celinda Lake said. "There is still time for him to do that, because the economy is the No. 1 thing people are paying attention to."

The president is working to correct that, launching a fresh effort Tuesday to define his second-term vision with a new minute-long television ad airing in all the key battlegrounds.

Romney aides, who have been gripped by an unfamiliar feeling of optimism and excitement since the first debate, say it's too late for the president to reinvent himself.

"The president being at 46, 47 percent, that would scare the crap out of me if I'm the incumbent," Romney adviser Russ Schriefer said of the president's approval rating, which has recently hovered just below 50 percent.

Romney's latest campaign theme -- that he is a firm and resolute leader with a clear plan to fix a rudderless economy -- infuriates Obama advisers, who scoff at the idea that someone who has veered wildly from message to message throughout his campaign is suddenly a more trustworthy option than the president.

But Republicans outside the campaign say Romney has finally put his finger on a credible message at precisely the right moment.

"If the election were held today, I think Obama might squeak out a win, but he is now playing defense and running a very small campaign," said Steve Duprey, a Republican power player in New Hampshire who advised John McCain's presidential campaign. "Contrast that with Romney, who sounds optimistic and sunny. People like to see someone who has momentum and see someone who has positive, sunny rhetoric."

Talk has percolated in Romney-world that a late advertising push might be possible in Democratic-leaning Michigan and Pennsylvania, where Obama has long been considered safe.

One high-ranking Romney official, granted anonymity to speak frankly about campaign tactics, admitted that Michigan is probably off the table because Democrats "have done such a job of sticking a knife in us on the auto bailout."

But Pennsylvania, with 20 electoral votes and no early voting, remains an intriguing smash-and-grab possibility for Romney media buyers if the polls there remain within the margin of error the week before Election Day.

Democrats call that talk nothing more than a head fake -- Obama campaign manager Jim Messina answered with a flat "no" when asked if Pennsylvania is a battleground state -- but the Romney campaign and the Republican National Committee have kept more than 60 staffers in the state since last spring.

The Obama team insists it always knew the contest was going to tighten in its final stage, though it's commonly acknowledged among Democrats that the president's dismal first debate showing was a colossal self-inflicted wound.

Despite the avalanche of ads currently swamping television airwaves, the race will now be decided by the "ground game," a fundamental but often little-understood aspect of campaigns focused on the mechanics of voter identification, persuasion and turnout.

Despite Republican advances since 2008 in field work and early voting, which started in Iowa in late September and is under way in five other swing states, few in either party question the supremacy of the Obama ground operation.

Obama supporters say their early investments in staff and field offices in key battlegrounds -- the campaign has been deeply embedded in Ohio, where it has over 130 offices, since the epic Democratic primary fight of 2008 -- will carry the day in November.