President Barack Obama, first lady Michelle Obama, former President Bill Clinton and his wife former Secretary of State Hillary Rodham Clinton, pause during a wreath laying ceremony in honor of President John F. Kennedy, Wednesday, Nov. 20, 2013, at Arlington National Cemetery in Arlington, Va. Friday will mark the 50th anniversary of the Kennedy assassination. (AP Photo/Pablo Martinez Monsivais)
The eternal flame burns atop at the gravesite of President John F. Kennedy at Arlington National Cemetery in Arlington, Va., Tuesday, Nov. 19, 2013. Friday, Nov. 22 will mark the 50th anniversary of Kennedy's assassinated in Dallas. (AP Photo/Carolyn Kaster)