On a 2007 visit to Savelugu Hospital in Ghana, President Jimmy Carter asks a group of children if they've had Guinea worm. A raised hand is a yes. Louise Gubb/Courtesy of the Carter Center hide caption

itoggle caption Louise Gubb/Courtesy of the Carter Center

Jason Carter, the eldest grandson of former President Jimmy Carter, is running to become Georgia's next governor. Erik S. Lesser /Landov hide caption

itoggle caption Erik S. Lesser /Landov

President Obama, former presidents George W. Bush, Bill Clinton, George H.W. Bush and Jimmy Carter attend the opening ceremony of the George W. Bush Presidential Center on Thursday in Dallas, Texas. The Bush library, which is located on the campus of Southern Methodist University, with more than 70 million pages of paper records, 43,000 artifacts, 200 million emails and four million photographs. Alex Wong/Getty Images hide caption

itoggle caption Alex Wong/Getty Images

V ice President Joe Biden, left, and President Obama embrace following Biden's vice-presidential nomination acceptance speech at the Democratic National Convention in Denver, Wednesday, Aug. 27, 2008. Paul Sancya/AP hide caption

itoggle caption Paul Sancya/AP