Vice President Joe Biden speaks to delegates at the Democratic National Convention in Charlotte, N.C., on Thursday, Sept. 6, 2012. (AP Photo/Lynne Sladky) President Barack Obama addresses the Democratic National Convention in Charlotte, N.C., on Thursday, Sept. 6, 2012. (AP Photo/Jae C. Hong) Vice President Joe Biden speaks to delegates at the Democratic National Convention in Charlotte, N.C., on Thursday, Sept. 6, 2012. (AP Photo/Lynne Sladky) President Barack Obama addresses the Democratic National Convention in Charlotte, N.C., on Thursday, Sept. 6, 2012. (AP Photo/Jae C. Hong)