The late preacher Billy Graham, left, and President Richard Nixon wave to a crowd of 12,500 in 1971 in Charlotte, N.C., at an event honoring Graham. AP hide caption
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Former Presidents Bill Clinton (left) and George Bush discuss their lives as current and former presidents at a leadership event at the George W. Bush Presidential Center in Dallas on Thursday. Tony Gutierrez/AP hide caption
In 2003, reporters listen to the then-newly released 240 hours of Nixon White House recorded conversations at the National Archives in College Park, Md. Joyce Naltchayan/AFP/Getty Images hide caption
Former President Bill Clinton gestures to the crowd during a campaign stop in Philadelphia for his wife, Hillary, on the day before the 2016 presidential election. Nicholas Kamm/AFP/Getty Images hide caption
Graham set out strict rules to keep his ministry from having any whiff of impropriety. That broad philosophy could be useful to White Houses. Stephen Chernin/Getty Images hide caption
The Clintons attend a 2011 dedication ceremony for a pedestrian bridge in Little Rock, Ark., located adjacent to former President Bill Clinton's presidential library. Brian Chilson/AP hide caption
Arkansas Weighs Whether To Remove The Clinton Name From Little Rock's Airport
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President Trump pauses before signing one of three executive actions in the Oval Office, Saturday. Alex Brandon/AP hide caption
Former President Bill Clinton plays with balloons onstage at the end of the fourth day of the Democratic National Convention at the Wells Fargo Center in Philadelphia in July. Aaron P. Bernstein/Getty Images hide caption
Christmas is coming, but Donald Trump still has a lot to say about November's election. Joe Raedle/Getty Images hide caption
Hillary Clinton chats with Goldman Sachs Chairman and CEO Lloyd Blankfein onstage during a panel discussion in 2014 of the Clinton Foundation's Clinton Global Initiative. Mark Lennihan/AP hide caption
There's Really No Comparison Between The Trump And Clinton Foundations
Former President Bill Clinton speaks at a campaign event for Democratic nominee Hillary Clinton at a college campus in Nevada. Ethan Miller/Getty Images hide caption
A screenshot from a 1995 video spoof of Forrest Gump, starring then-first lady Hillary Clinton. mustloveclintons/YouTube hide caption
Hillary Clinton has defended the Clinton Foundation against allegations that it was a front for a "pay to play" scheme while she was secretary of state. Scott Eisen/AP hide caption
'Saving Lives' Or 'Selling Access'? Explaining The Clinton Foundation
Democratic presidential candidate Hillary Clinton speaks at a rally at Osceola Heritage Park, in Kissimmee, Fla. Andrew Harnik/AP hide caption