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George H.W. Bush, Ross Perot

FILE - In this Oct. 15, 1992, file photo President George H.W. Bush looks at his watch during the 1992 presidential campaign debate with other candidates, Independent Ross Perot, top, and Democrat Bill Clinton, not shown, at the University of Richmond, Va. They spend hours mastering policy. Learning to lean on the podium just so. Perfecting the best way to label their opponents as liars without whining. But presidential candidates and their running mates often find that campaign debates turn on unplanned zingers, gaffes or gestures that speak volumes. Debate wins and losses often are scored based on the overall impressions that candidates leave with voters. In the history books, though, small debate moments often end up telling the broader story. (AP Photo/Ron Edmonds, File)

Great debate moments

By Claudine Zap

The first debate between Republican presidential candidate Mitt Romney and President Barack Obama will be held on Wednesday. While the candidates prepare their talking points, we look back at some of the more memorable moments from past presidential face-offs. A zippy zinger can get serious airplay even after the actual debate is over, but so can an ill-timed gaffe. Here, some of the top moments.