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U.S. Secret Service agents stand watch as Republican presidential candidate and former Massachusetts Gov. Mitt Romney and vice presidential candidate Rep. Paul Ryan, R-Wis., campaign at the Celina Fieldhouse in Celina, Ohio, Sunday, Oct. 28, 2012. (AP Photo/Charles Dharapak)

Mitt Romney

Yahoo News

Highlights from Republican presidential nominee Mitt Romney's 2012 campaign trail.