The rally was also a last public appearance before the Republican National Convention begins Monday in Tampa, Fla., The Washington Post reported. More than 5,000 supporters packed a park in Powell, an affluent suburb of Columbus.
Romney, the presumptive Republican nominee, attacked a speech President Obama has yet to give -- his acceptance of the Democratic nomination at the party's convention in Charlotte, N.C. He said Obama would have "marvelous things to say."
"They've experienced the last four years, and they know if they reelect him they'll get four more years of the same," Romney said. "It is not his words that people have to listen to; it is his action and his record, and if they look at that, they'll kick him out of the office and put people into the office that will actually get America going again."
Ryan, a Wisconsin congressman, served as Romney's warm-up act. He reminded the crowd of the economic troubles of recent years, including the drop in household income and rising unemployment.
Obama won Ohio by 5 percentage points four years ago, but the state appears likely to be a toss-up this time.