Santorum said his conservative message has been consistent, the Los Angeles Times reported.
"Ladies and gentlemen," Santorum told hundreds of supporters and students at a Christian school in Miamisburg, a suburb of Dayton. "I come to the people of Ohio as a candidate who shouldn't be here, who shouldn't be here, if you looked at any political expert and you looked at the money that's been spent and the airtime that's been given, but we're here for a reason -- because I'm experienced, I'm principled, I'm values, energy, enthusiasm and grit."
Santorum said if he had the same resources as Romney, he would be running away with the race, the Times said.
"This race isn't going to be won or lost in the fall on money," he said, "this race is going to be won or lost on someone who can capture the imagination of the American people, someone who can go out and articulate that vision for where our country must go if we're going to be free and safe and prosperous."
Romney, meanwhile, spoke at a town hall event in Youngstown to a crowd of 500, The (Cleveland) Plain Dealer reported.
"I hope I get the support of the people in Ohio tomorrow," the former Massachusetts governor said. "If I do, I believe I get the nomination."
The Plain Dealer said a new round of polls out Monday confirmed a tight race between Romney and Santorum, a former Pennsylvania senator, in Ohio, the most important of the Super Tuesday states.
A Quinnipiac University poll indicated Romney leading Santorum 34 percent to 31 percent, within the poll's 3.6 percent margin of error. But the newspaper said a Quinnipiac poll last week showed Santorum leading Romney by 7 percentage points.