clinton

Barack Obama, Michelle Obama, Michael Bloomberg, Bill Clinton, Hillary Rodham Clinton...President Barack Obama and first lady Michelle Obama, along with former Secretary of State Hillary Rodham Clinton and former President Bill Clinton tour the Memorial Hall at the National September 11 Memorial Museum with former New York Mayor Michael Bloomberg, Thursday, May 15, 2014, in New York.

Carolyn Kaster/AP

President Barack Obama and first lady Michelle Obama, along with former Secretary of State Hillary Rodham Clinton and former President Bill Clinton tour the Memorial Hall at the National September 11 Memorial Museum with former New York Mayor Michael Bloomberg, Thursday 

President Barack Obama stands with, from second from left, former Presidents George W. Bush, Bill Clinton, George H.W. Bush, and Jimmy Carter at the dedication of the George W. Bush presidential library on the campus of Southern Methodist University in Dallas, Thursday, April 25, 2013.

Charles Dharapak/AP

President Barack Obama stands with, from second from left, former Presidents George W. Bush, Bill Clinton, George H.W. Bush, and Jimmy Carter at the dedication of the George W. Bush presidential library on the campus of Southern Methodist University in Dallas on Thursday.