President Richard Nixon famously declared "Well, I'm not a crook" during a televised press conference on November 17, 1973. Questions had been intensifying about his role in the 1972 break-in at the Democratic National Committee headquarters in the Watergate complex and subsequent cover-up efforts as well as his personal finances. Less than nine months later, Nixon resigned to avoid impeachment.
His full quote was : "People have got to know whether or not their president is a crook. Well, I'm not a crook. I've earned everything I've got". The ongoing investigations, the "Saturday Night Massacre," and the eventual revelation of the White House tapes (including an incriminating 18 1/2-minute gap) forced his resignation.