BOCA RATON, Fla. — Their debates now history, President Barack Obama and Republican Mitt Romney on Tuesday open a two-week sprint to Election Day powered by adrenaline, a boatload of campaign cash and a determination to reach Nov. 6 with no would-have, should-have regrets in their neck-and-neck fight to the finish.

From here, the candidates will vastly accelerate their travel, ad spending and grass-roots mobilizing in a race that’s likely to cost upward of $2 billion by the time it all ends.

All the focus now is on locking down support in the nine states whose electoral votes are still considered up for grabs: Colorado, Iowa, Florida, New Hampshire, Nevada, North Carolina, Ohio, Wisconsin and Virginia. No surprise then, that Obama campaigns Tuesday in Florida and Ohio while Romney heads West to Nevada and Colorado.

Asked Tuesday whether the race comes down to Ohio, Virginia and Florida as some observers have suggested, Vice President Joe Biden described the three as “critically important.” He predicted victory in Ohio and Florida — without mentioning Virginia.

“Look, this is going to be close,” Biden said in an appearance on NBC’s “Today” show. “We always knew at the end of the day this was going to be a close race, no matter who the Republicans nominated.”

Neither candidate scored a knockout punch in their third and last debate Monday, as both men reined in the confrontational sniping that had marked their last testy encounter. And though the stated topic this time was foreign policy, both kept circling back to their plans for strengthening the fragile U.S. economy — Job 1 to American voters.

Closing out their trio of debates, Obama concisely summed up this pivot point in Campaign 2012: “You’ve now heard three debates, months of campaigning and way too many TV commercials. And now you’ve got a choice.”

The president framed it as a choice between his own record of “real progress” and the “wrong and reckless” ideas of Romney.

Romney countered by sketching “two different paths” offered by the candidates, one of decline under Obama and one of brighter promise from himself.

“I know what it takes to get this country back,” he pledged.

With polls showing the race remains incredibly tight, first lady Michelle Obama made a prediction before the candidates left Florida that neither side would dispute: “This election will be closer than the last one — that’s the only guarantee.”

Obama made it look easy in 2008. He won 365 electoral votes to 173 for Republican John McCain. And he got 53 percent of the popular vote, to 46 percent for McCain.