Vice President Joe Biden speaks as Republican Rep. Paul Ryan and moderator Martha Raddatz listen during the vice presidential debate at Centre College on Thursday in Danville, Ky. Michael Reynolds/Pool/Getty Images hide caption

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Tonight's faceoff between Vice President Joe Biden (right) and GOP Rep. Paul Ryan of Wisconsin will likely be an important stage-setter for next week's second presidential debate. Jose Luis Magana/Thanassis Stavrakis/AP hide caption

itoggle caption Jose Luis Magana/Thanassis Stavrakis/AP