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President Obama on Sunday asked Americans for more time to finish what he started while Mitt Romney argued the country needs a change in leadership – as both candidates distilled the closing arguments in the final weekend of the 2012 campaign.

Obama and Romney held morning events and will go late into the night -- rallying in one battleground state, then dashing onto an airplane to reach another with two days left before Election Day.

“After all we have been through, we can’t give up now,” Obama said during an outdoor event in Concord, N.H., attended by more than 14,000 people. “I’m not ready to give up the fight.”

At practically the same time, Romney argued the president had four years to improve the country and warned that another Obama term might result in more economic decline.

“The same course we’ve been on, will not lead to a better destination,” Romney told a crowd of about 4,400 in Des Moines, Iowa. “Unless we change course, we may be looking at another recession.

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    "The question of this election comes down to this: Do you want four more years like the last four years, or do you want real change? President Obama promised change, but he couldn't deliver it. ... He's got excuses. I've got a plan."

    The candidates are making their closing arguments Sunday in six key battleground states.

    Romney also will hold rallies in Ohio and Pennsylvania, while the president visits Florida, Ohio and Colorado.

    The candidates are once again tied nationally with two days remaining before Election Day, according to a Washington Post-ABC News tracking poll released Sunday.

    Among likely voters, Obama and Romney are deadlocked at 48 percent. And for the first time this year, they are tied among independents voters, at 46 percent each, the poll says.

    Romney’s position going into Election Day is in part the result of how he performed in the three presidential debates, The Post reports.

    Before the candidates hit the trail, their top campaign officials expressed confidence about victory Tuesday and argued about who had the edge in battleground states and in early voting.

    “They are in deep trouble,” Obama senior campaign adviser David Axelrod said on “Fox News Sunday.” “They understand the battleground states where they’ve been working is not working out for them.”

    Rich Beeson, Romney’s political director, said the campaign has found success in a final get-out-the-vote effort that reached out to people who are not core Republicans or vote regularly.

    "We've done a much, much better job of getting our low propensity voters out to vote," he told Fox. "And we've got all of our high propensity voters ready to go vote on Election Day."

    On the criticism that the campaign has failed to lock down Republican-friendly Florida, Beeson said: “For them to go down and spend more money down there is a little bit like Barack Obama's government right now. They want to throw money at the problem and hope it fixes it, but at the end of the day, Gov. Romney will carry Florida by a significant margin.”

    Obama's campaign is mobilizing a massive get-out-the-vote effort aimed at carrying the Democrat to victory, as Romney makes a late play for votes in Democratic-leaning Pennsylvania.

    A new poll in The Pittsburgh Tribune shows the race for Pennsylvania’s 20 electoral votes locked up at 47 percent in its final week. The poll by Susquehanna Polling & Research surveyed 800 likely voters from Thursday through Saturday and most of the interviews occurred after superstorm Sandy inundated eastern and central Pennsylvania. The poll’s error margin is 3.46 percentage points, according to the newspaper.

    Both campaigns have for the past few days been 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 presidential nominee was cutting away briefly Sunday from the nine or so competitive states that have dominated the candidates' travel itineraries this fall. He and running mate Rep. Paul Ryan have an early-evening event planned in Morrisville, Pa. -- Romney’s first rally in the state this fall.

    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.

    The Republican ticket cast the late push into the Keystone State 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.

    Democrats have a million-voter registration advantage in Pennsylvania. Obama senior adviser David Plouffe said that means Romney would have to win two-thirds of the state's independents, a prospect he called "an impossibility."

    The president caught a few hours of sleep back at the White House Saturday night before hitting the campaign trail again Sunday. After Marine One lifts off from the South Lawn Sunday morning, Obama won't return to the executive mansion again until after Election Day.

    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 Clinton drew 24,000 people to an outdoor rally in Bristow, Va., on a cold Saturday night.

    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.

    Romney 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.

    The Associated Press contributed to this report.