"In a democracy, you can't just threaten to jail your opponents," Mr. Obama said, referring to Trump's line in recent days that Clinton should be in jail over her email server.
The President also noted the speech of his wife this week in New Hampshire, where she said Trump's vulgar remarks about women had shaken her "to my core."
"She was also talking on behalf of men who know we're better than this," the President said.
Trump was in both Columbus and Cincinnati on Thursday, as the two parties fight over this key state - the polls have been mixed in recent weeks.
Early in Mr. Obama's speech today, he was interrupted by a Trump protester.
"If you're confident about the other guy - just go to his rallies," the President said to applause.
"You don't have to spend time over here; go knock on some doors for your guy - that's a better way for you to spend your time - unless you're being paid to be here," he added.