Obama -- appearing at a late-night even in Des Moines, Iowa, first lady Michelle Obama called "the final event of my husband's final campaign" -- said he is "not ready to give up on the fight."
"I've got a lot more fight left in me. ... I need you to still have some fight in you, too," he said.
"I've come back to Iowa one more time to ask for your vote. I came back to ask you to help us finish what we started. Because this is where our movement for change began. ...
"When Americans come together, determined to bring about change, nobody can stop us. We cannot be stopped. And after all we've been through together, after all that we've fought through together, we cannot give up on change now.
Obama said every American should have a shot at a great education and said he wants to create the "energy jobs of tomorrow."
"Change is turning the page on a decade of war so we can do some nation building here at home," Obama said, adding middle-class Americans need a "champion" to represent them in the Oval Office.
Romney, campaigning in Orlando, Fla., said, "Look, we -- we have one job left and that's to make sure that on Election Day, we get -- make certain that everybody who's qualified to vote gets out to vote."
The former Massachusetts governor said the campaign was "about America and about the future we're going to leave our children."
A Romney victory, he said, means "a new tomorrow ... a better tomorrow. This nation is going to begin to change for the better tomorrow."
"You hoped that President Obama would live up to his promise to bring people together and to solve problems," Romney told an enthusiastic crowd in one of the battleground states. "He hasn't. I will."
Later on the stump in Lynchburg, Va., Romney told the audience that anyone undecided should look "look beyond the speeches and the ads and all the attacks because talk is cheap."
Anyone undecided should "look at the record. A record is real and it's earned with real effort," Romney said.
He again attacked Obama, saying, "The president promised change, but change can't be measured in speeches, it's measured in achievement. And look at his record, four years ago, candidate Obama promised he'd do so very much, but he fell so very short."
At an earlier event in Madison, Wis., Obama admitted he had a hard act to follow after singer-songwriter Bruce Springsteen, who also introduced Obama in Iowa, left the stage.
"We've made progress these last four years. But the reason we're all gathered here -- in addition to listening to Bruce -- is because we know we've got more work to do. We've got more work to do," Obama said. "As long as there's a single American who wants a job but can't find one, our work is not yet done. As long as there are families working harder and harder but still falling behind, we've got more work to do. As long as there is a child anywhere in Madison, in Wisconsin, in America, who's languishing in poverty and barred from opportunity, our work is not yet done. The fight goes on."
Criticizing Romney on a number of fronts, including not fully revealing his policy plans and repositioning the "same old" economic policies of the George W. Bush administration, Obama said, "So, Wisconsin, we know what change is. We know what the future requires. But we also know it's not going to be easy."
He said he ran in 2008 because "the voices of the American people -- your voices -- had been shut out of our democracy for way too long by lobbyists and special interests and politicians who will say and do anything just to keep things the way they are, to protect the status quo. And the status quo in Washington is fierce."
Obama appealed to Wisconsinites to vote to ensure "your voices are heard. We have come too far to turn back now."
"And if you're willing to work with me again, and knock on some doors with me, make some phone calls for me, turn out for me, we'll win Wisconsin. We'll win this election. We'll finish what we started."
During a campaign visit in Sterling, Va., Vice President Joe Biden said he was "feeling good" about the race on the last day of the campaign.
"You've been with me long enough to know that I'm always optimistic," Biden told reported. "But I really do feel good."
He offered his assessment of some of the battleground states:
"I think we'll win Ohio. I think we'll win Wisconsin. I think we'll win Iowa. I think we'll win Nevada. I think we'll win New Hampshire. I think Florida will be close but I think we have a real shot at winning. And this state [Virginia], we've got a clear shot at winning."
Stephanie Cutter, Obama's deputy campaign manager, told CNN Monday night Pennsylvania has "tightened" ahead of Election Day. The Romney campaign was making a final push to win the Keystone State, where former President Bill Clinton was scheduled to make his final appearance on behalf of Obama.