President Obama walks from the White House to Marine One on Friday. In an interview Thursday with NBC News, he apologized for breaking a promise regarding the Affordable Care Act. J. Scott Applewhite/AP hide caption

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Former President George W. Bush speaks alongside former first lady Laura Bush during the opening ceremony of the George W. Bush Presidential Library and Museum on Thursday in Dallas. Kevork Djansezian/Getty Images hide caption

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President Barack Obama gestures toward former President George W. Bush, former first lady Laura Bush and first lady Michelle Obama, at the White House in Washington, Thursday, during a ceremony where the Bushs' portraits were unveiled. Charles Dharapak/AP hide caption

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Oct. 7, 2001: President George W. Bush poses for a photo in the Treaty Room of the White House after announcing airstrikes on on Afghanistan.

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