Watergate is the gold standard of botched cover-ups with disastrous consequences. In June 1972, police arrested five burglars at the Watergate hotel and office complex in Washington, where they were attempting to place listening bugs in the offices of the Democratic National Committee. It quickly became apparent that the burglars had links to President Richard Nixon — one of them, Bernard Barker, had a $25,000 check from Nixon's campaign in his bank account.
By October, an FBI investigation had determined that the break-in was part of a massive campaign of political spying and sabotage on behalf of Nixon — who, somehow, still managed to win re-election in a landslide. But as Congressional investigators started digging into the case in 1973, Nixon and his aides dug in their heels —even after former White House counsel John Dean revealed that he'd had 35 discussions with the president about the cover-up.
Nixon resisted turning over secret tapes of White House meetings, and even fired Archibald Cox, the special prosecutor that his administration had appointed to at least give the appearance of trying to clean house. Eventually, when Nixon turned over a crucial tape, it had a mysterious 18-and-a-half minute gap in it. At that point, despite his earlier protestations of "I am not a crook," nobody believed him. In July 1974, after the House of Representatives passed the first of three articles of impeachment against him, Nixon finally quit. His successor, Gerald Ford, pardoned him, ensuring that he would avoid being the first U.S. president to go to prison [source: Washington Post].