Columbus, Ohio (CNN) -- President Obama pleaded with Democratic voters to keep hope alive and warned about Republicans making congressional gains in an Ohio speech Sunday that comes just weeks before the midterm elections.
"Everybody said, 'No you can't' and in 2008 you showed them, 'Yes we can,' " Obama told tens of thousands of supporters at Ohio State University in Columbus. "In two weeks, you have the chance to say once again, 'Yes we can.'"
Obama repeatedly urged the crowd to try to recreate the aura of 2008, when he rode a Democratic wave into the White House and his party gained seats on Capitol Hill.
The president focused mostly on the economy Sunday, arguing that his policies had staved off a second Great Depression and warning that a Republican return to power would revive the economic policies of the early 2000s.
Striking a populist tone, Obama said such policies would favor powerful corporations over middle-class Americans. Republican gains would lead to rollbacks in federal health care and education assistance, he said, while wealthy Americans would reap tax cuts and big companies would enjoy lighter regulation.
"They'll tell you its the ownership society, but basically it's 'You're on your own,'" Obama said, at what was officially a Democratic National Committee rally. "If you lose your job, you're on your own. If your child doesn't have health care, tough luck, you're on your own."
"This is the same theory they have been peddling for years and it's up to you to tell them we do not want what they are selling," Obama said later. "We've been there before and we're not going back."
Obama's stop in Ohio is one in a series of appearances he's making in states that he easily took two years ago but where Democrats are struggling to hold onto gubernatorial mansions and House seats ahead of next month's midterm elections.
In the Buckeye State, Democratic Gov. Ted Strickland -- who spoke before Obama on Sunday -- is locked in a tight re-election race with former Rep. John Kasich, a Republican.
Ohio Reps. John Boccieri, Steve Driehaus, Mary Jo Kilroy and Zack Space -- all Democrats -- are at risk of losing their seats next month, political analysts say.
First lady Michelle Obama appeared with the president on Sunday night, in their first day of joint campaigning since 2008.
Mrs. Obama said that she'd avoided the campaign trail "since a little campaign you might remember a a couple of years ago."
"If you are still as fired up as you were in two years ago then I know we can keep bringing about the change that I know -- that we all know -- can keep that American dream alive," she said.
At a Cleveland fundraiser earlier in the day, Mrs. Obama introduced her husband as "the love of my life, even though he doesn't always think it. And more importantly, the president of the United States."
"It is not true that more importantly I am the president of the United States," the president replied when he got the microphone. "More importantly, I am Michelle Obama's husband, and Malia and Sasha's father, and Michelle has put up with me through thick and thin, and I'm grateful for her each and every day."
CNN Senior White House Correspondent Ed Henry contributed to this report.