Obama also accused Clinton of supporting the North American Free Trade Agreement (NAFTA), which her husband, former President Bill Clinton, championed when he was in office.

That agreement is extremely unpopular in Ohio, which has suffered an exodus of blue-collar jobs.

Clinton said she had always opposed NAFTA, which Obama said was news to him. He pointed out that Clinton praised the deal as good for New York during her senatorial campaign.

US Democratic presidential candidates Senator Hillary Clinton (D-NY) and Senator Barack Obama (D-IL) square off in the last debate before the Ohio primary in Cleveland, Ohio, February 26, 2008. (Xinhua/Reuters Photo)

The contenders also renewed their argument over who has the best judgment or whether experience in office matters more and exchanged some jobs.

"He's to be commended for having given the speech' (in 2002) in opposition to going to war with Iraq," Clinton said of Obama. But she pointed out that after Obama entered the Senate in 2005, "we've voted the same. ... When it wasn't a speech, where it was action, where was the difference?"