President Obama greets supporters during a campaign rally on Saturday in Milwaukee. Scott Olson/Getty Images hide caption

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President Obama toasts others at the Dubliner Restaurant and Pub in Washington, D.C., on March 17. Joshua Roberts/Getty Images hide caption

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Republican presidential nominee Mitt Romney campaigns at PR Machine Works in Mansfield, Ohio, on Monday. Charles Dharapak/AP hide caption

itoggle caption Charles Dharapak/AP