Richard Nixon
Nixon was re-elected by a landslide in 1972 with most Americans approving of him, but soon after, Nixon's reputation would be destroyed and most Americans would disapprove of him.  Due to a scandal called "Watergate" during which Nixon attempted to protect (or possibly ordered) men to burglarize the Democratic National Headquarters, Congress was going to put him on trial in a process called impeachment (to remove him from power). Nixon tried to cover up the scandal, but eventually, the Supreme Court ordered him to send his taped conversations (which included him talking about covering up Watergate) to them.  Alexander Haig thought Nixon would be convicted and kicked out of office. To prevent this, Nixon resigned (quit) the presidency in 1974.