"All they've got is the same old stuff that they were peddling over the last decade," he said of Republicans. "I just don't want to relive the past." He said: "The other side is betting on amnesia. It is up to you to show them that you have not forgotten."
Obama rallied in Minneapolis to help former Sen. Mark Dayton in his race for governor against Republican state legislator Tom Emmer and the Independence Party's Tom Horner, a public relations executive and political pundit. Republican Gov. Tim Pawlenty's second term runs out in January.
"Mark Dayton has spent his life working for Minnesota and now I need all of you to fight for Mark Dayton," Obama told a crowd estimated at 11,000 by the University of Minnesota, where he spoke.
It's been a grueling four days of campaigning and fundraising by the president, who since Wednesday had touched down in Oregon, Washington state, California and Nevada. He has been helping congressional allies, such as Senate Majority Leader Harry Reid of Nevada, in tight races.
Cheered at large rallies at every stop, Obama begins his basic speech with some flattering talk about the local candidate. Then he launches into his message that voting Republican would be a mistake for the country.
"This election is a choice between the policies that got us into this mess and the policies that are leading us out of it," he told the Minnesota rally.
Voters are angry about the economy, unemployment and other issues and, according to polls, seem intent on taking out their frustrations on Democrats -- the party in power at both ends of Pennsylvania Avenue -- on Nov. 2.
But Obama is trying to remind the broad coalition that helped elect him in 2008 -- women, Hispanics, minorities, and young voters -- that change has always been slow to come but is coming, so they should not give up.
"Don't let them tell you that change isn't possible," Obama said. "It's just hard, that's all."
Pawlenty, who has said he'll decide next spring whether to run for the Republican presidential nomination in 2012, released a video welcoming Obama to Minnesota with a tongue-in-cheek vocabulary lesson in the use of local expressions like "uffdah" and "yikes."
"As in the sentence, 'The federal deficit was over a trillion dollars the last two years, and will be next year, too. Yikes!"' Pawlenty said. The video was posted on YouTube.
Before leaving Minneapolis, Obama also was helping to raise about $600,000 for House Democrats at a fundraiser attended by House Speaker Nancy Pelosi, Rep Chris Van Hollen, D-Md., chairman of the House Democratic campaign effort, and others.
Obama was returning to Washington late Saturday and will head out again next week for more campaigning.
On Monday, he'll be in Rhode Island to help raise more money for House Democrats. He is scheduled to spend the rest of the week in Washington, including an appearance Wednesday on "The Daily Show" with Jon Stewart.
He plans to travel again the weekend before the election, making a final get-out-the-vote push at events in Bridgeport, Conn., Chicago, Philadelphia and Cleveland.