WASHINGTON -- Just two days from the finish, President Barack Obama's campaign is mobilizing a massive get-out-the-vote effort aimed at carrying the Democrat to victory, as Republican Mitt Romney makes a late play for votes in Democratic-leaning Pennsylvania.

Both campaigns were predicting wins in Tuesday's election. Obama was closing out the campaign with an apparent edge in some key battleground states, including Ohio. But Romney's campaign was projecting momentum and banking on late-breaking voters to propel him to victory in the exceedingly close race.

"Words are cheap and a record is real and it's earned with effort," Romney said Saturday, making a final appeal to voters in Colorado.

The Republican was cutting away briefly Sunday from the nine or so competitive states that have dominated the candidates' travel itineraries. Romney, along with running mate Paul Ryan, had an early evening event planned in Morrisville, Pa., his first rally in the state this fall.

"This is a desperate ploy at the end of a campaign," said David Plouffe, a top adviser to Obama's campaign, on ABC's "This Week," arguing that Romney would have to win 2 out of 3 independents to pick up Pennsylvania. "He's not going to do that anywhere, much less Pennsylvania. So the truth is, they are throwing some ads up and Gov. Romney is traveling in the state he's not going to win."

Democrats have a million-voter registration advantage in Pennsylvania.

Romney's visit follows the decision by his campaign and its Republican allies to put millions of dollars in television advertising in Pennsylvania during the race's final weeks. Obama's team followed suit, making a late advertising buy of its own.

"You saw the differences when President Obama and I were side-to-side in our debates," Romney says in a new TV ad filmed at an Ohio rally and released Sunday. "He says it has to be this way. I say it can't stay this way. He's offering excuses. I've got a plan. I can't wait for us to get started."

The campaign did not say where the ad would run.

The Republican ticket cast the late push into Pennsylvania as a sign that Romney had momentum and a chance to pull away states that Obama's campaign assumed it would win handily. The president's team called the move a "Hail Mary" and a sign Romney still doesn't have a clear pathway to reaching the required 270 Electoral College votes.

The president caught a few hours of sleep back at the White House Saturday night before hitting the campaign trail again Sunday. When Marine One lifted off from the South Lawn Sunday morning, it was the last time Obama would see the executive mansion until after Election Day.

Obama had a full schedule, with campaign stops Sunday in New Hampshire, Florida, Ohio and Colorado.

The president's rallies are aimed at boosting Democratic enthusiasm and motivating as many supporters as possible to cast their votes, either in the final hours of early voting or on Tuesday, Election Day. Persuading undecided voters, now just a tiny sliver of the electorate in battleground states, has become a secondary priority.

Obama and former President Bill Clinton drew 24,000 people to an outdoor rally in Bristow, Va., on a cold Saturday night.

Clinton, his voice hoarse after a week of campaigning, said he had "given my voice in the service of my president." But that didn't stop him from launching into a 30-minute defense of Obama and his economic policies.

He also slammed Romney for his shifting positions, saying "He could be the chief contortionist for Cirque de Soleil."

Obama, who spoke second, embraced Clinton as he walked on stage. The president said at this stage of the campaign, he was largely "a prop" and the race was in the voters' hands.

"The power is not with us anymore," he said. "It's all up to you."

Obama's campaign said it had registered 1.8 million voters in key battleground states, nearly double the number of voters they registered in 2008. Campaign officials said volunteers had made 125 million personal phone calls or door knocks with voters.

Romney has also attracted large crowds in the final weekend of campaigning. His rally in Ohio on Friday drew more than 20,000 people.

"When I look at being on the road for three days with Gov. Romney and the crowds, when I look at the undecideds, I believe that Gov. Romney will not only win on Tuesday, I believe he could win decisively," Romney adviser Ed Gillespie said on ABC's "This Week."

The Republican nominee has been using teleprompters to deliver his final campaign speeches. He's claiming the mantle of change - and highlighting what he says was a bipartisan record as governor of Massachusetts.

In addition to Pennsylvania, Romney will campaign Sunday in Iowa, Ohio and Virginia.