She highlighted the president's work in office, including the auto bailout, health care overhaul, ending the war in Iraq, killing Osama bin Laden and cutting taxes for small businesses.
"Teachers and firefighters shouldn't be paying higher tax rates than millionaires and billionaires," she yelled to applause.
The first lady repeated the speech Saturday night at Kenyon College in Gambier in eastern Ohio. The college is an important footnote in battleground Ohio's political history: Eight years ago, a problem with Gambier voting machines created the nation's longest voting lines on election night, with many students and residents waiting until well past midnight to vote.
Michelle Obama played to the college crowd, encouraging them to consider a strategic change to their weekend plans.
"If you've got any dates planned, bring them to the campaign office," she said to applause. "Do something real clever like that."
One Kenyon student, Westchester, N.Y., resident Amy Morgan, said she had voted Friday.
"I early voted, in Ohio, because it's a swing state," said Morgan, 20, a junior biology major.
Ryan campaigned in Ohio and Pennsylvania, where he took issue with Obama's comment to supporters that voting would be their "best revenge."
"We don't believe in revenge; we believe in change and hope," Ryan said in Marietta in southeast Ohio. "We actually do."
Ohio Secretary of State Jon Husted announced that as of Friday, more than 1.6 million Ohioans have already voted, including 1.1 million by absentee ballot and almost 500,000 at early voting centers.
Associated Press writers Amanda Lee Myers in Oxford and Andrew Welsh-Huggins in Gambier contributed to this report.