Dr. Sanjay Gupta reports on the toll that serving as president has taken on the health of past commanders-in-chief. Also: what the medical records of John McCain and Barack Obama say about their readiness to serve as president. Included: interviews with former White House press secretaries Ari Fleischer, Joe Lockhart, Jody Powell and Ron Nessen, former Reagan White House chief of staff Kenneth Duberstein and former White House physicians Rob Darling, Burton Lee and Connie Mariano.