Rep. Paul Ryan greets supporters during a campaign rally Sunday in Waukesha, Wis. Saul Loeb/AFP/Getty Images hide caption

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Who will be Romney's VP? The naming of his running mate is likely going to come in mid-August, after his foreign trip and the conclusion of the Olympics. Ken Rudin collection hide caption

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Vice President Joe Biden is interviewed by NPR's Robert Siegel in the Secretary of War Suite of the Eisenhower Executive Office Building, Dec. 13. David Lienemann/The White House hide caption

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Vice President Joe Biden smiles after filing papers for President Obama to be on the N.H. primary ballot. (AP Photo/Jim Cole)

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