MORRISVILLE, PA. — And now it is closing time. On Monday, in the final hours of their 17-month, nearly $3 billion marathon, the two candidates and their running mates are scheduled to hold 14 events across eight states.

For Republican challenger Mitt Romney, this last full day of campaigning is aimed at achieving what he has seemingly been unable to do over the first 522 days: overcome President Barack Obama’s razor-thin but steady leads in the states where the election will be decided.

On Sunday, it appeared that Romney’s task was getting a little harder.

A pair of national polls seemed to show that it was Obama who had a bit of momentum in the race’s last weekend. A Washington Post-ABC News poll showed the president at 49 percent to Romney’s 48 percent. The tracking poll has had both candidates locked within a narrow band for weeks, although Romney held a brief three-point edge in late October.

Another poll, released Sunday by the Pew Research Center, found Obama with a three-point lead nationwide among likely voters, 48 percent to 45 percent. A week ago, the same poll had the two candidates tied.

The Pew poll found that Hurricane Sandy may have given Obama a boost: Sixty-nine percent of likely voters approved of the president’s handling of the storm.

Meanwhile, a poll late Sunday by CNN showed the race deadlocked at 49 percent.

In addition to the polls, data on early voting seemed to show Democrats with an edge in several key states, although not as wide as the advantages Obama held four years ago.

Nonetheless, Romney and his aides said they were confident of victory. The Republican made a striking gesture of that confidence by visiting Pennsylvania, a state long assumed to be in Obama’s column and one that has not voted for a GOP presidential candidate in more than two decades. A top aide, Ed Gillespie, said that Romney has “expanded” the map of this election and expects to compete in the Keystone State.

Taking the stage to the “Rocky” theme before a crowd of about 30,000 in Morrisville, Romney declared that “this audience and your voices are being heard all across the nation . . . We’re taking back the White House, because we’re going to win Pennsylvania!”

On Sunday, the two campaigns held 14 events in eight states, including six in the battleground of all battlegrounds, Ohio. At one point, the two sides got close enough to see each other: As Air Force Two prepared to take off from the Cleveland airport on Sunday afternoon, Vice President Joe Biden spotted Romney’s campaign plane across the tarmac.

For both candidates, it was a day of big crowds - and final goodbyes.

In the morning, Obama visited New Hampshire for the seventh time during the general-election season after campaigning here extensively four years ago. This, presumably, was his last visit as a candidate. He spoke to a crowd of 14,000 in Concord, the state capital, with former President Bill Clinton.

“I know you guys — you saw a lot of me” in 2008, Obama told the audience. “And back then, we talked about change we can believe in. But I said to people, you know: ‘I’m not just talking about changing parties or changing presidents. I’m talking about changing how our politics works.’ “

Later Sunday, the president made his last stops in Florida and in Colorado. He also visited Ohio — but he will be back. On Monday, Obama will return for a rally in Cincinnati and will also travel to Wisconsin and Iowa, touching on the Midwestern trio that could provide his path to victory. At day’s end, he will return to his home town, Chicago, for Election Day.

Romney on Sunday made his last stop in Iowa after at least 14 trips there during the general-election campaign and many, many more before that, leading up to the 2008 and 2012 caucuses.

“Talk is cheap, but a record is real, and it’s earned with real effort,” Romney told a boisterous crowd of 4,000 at the Hy-Vee Hall in downtown Des Moines. He reprised a common stump-speech appeal, asking his supporters to reach out to friends and neighbors who may still be undecided. “You can’t measure change in speeches. You measure change in achievements,” he said.

Romney also visited Ohio on Sunday, speaking to 6,000 in Cleveland. At one point, he started to make an argument by saying, “If the president were to be re-elected . . . “

He was interrupted by boos.

“It’s possible,” he told the crowd in response, “but not likely.”

On Monday, Romney will go to Ohio one last time — making at least his 44th trip there during the general-election campaign. His itinerary also includes two stops in Virginia, one in Florida and a last, late-night rally in Manchester, N.H. Romney will then return to his home outside Boston for Election Day.

This weekend, new polls seemed to show that Romney had made little progress on the central mission of his campaign: to wrest these battleground states away from Obama.

In Iowa, a Des Moines Register poll gave Obama the edge, 47 percent to 42 percent. In Ohio, a Columbus Dispatch survey put the president two points ahead. If Obama wins those two states, he will need just one more swing state — even tiny New Hampshire — to win another term.

For Romney, some of the weekend’s best news came from New Hampshire, where a WMUR Granite State Poll released Saturday found the candidates tied. The same poll showed Obama with a nine-point lead in October.

For many voters, of course, the election is over. In the Post-ABC poll, 27 percent of all likely voters said they had cast their ballots already. In some battleground states, the numbers are even higher: In Nevada, the votes already cast are equal to 72 percent of the total vote in 2008. In Colorado, the figure is 68 percent.

For now, it’s impossible to know whom these early voters chose. But some states have released breakdowns by party.

In Iowa, Democrats hold an 11-point advantage in early voting, although that’s down from 18 points in 2008. In Florida, Democrats won by nine points four years ago but lead by only three points this year. And in Colorado, where Democrats had a two-point advantage in 2008, they currently trail by two.

Ohio doesn’t have traditional party registration. But outside polling has consistently shown Obama winning early voters there by double digits. About a quarter of likely voters in the state have already cast ballots.