Most Americans on this site are probably familiar with the Watergate Scandal. In 1972, several burglars were arrested, attempting to wiretap and steal documents from the DNC. What's more, these burglars are purported to have links to President Richard Nixon himself. After the incident, Nixon attempted to cover up these happenings, but obviously failed to do so. He resigned in '74, leaving then vice-president Gerald R. Ford the new leader of the Free World.
Ford pardoned Nixon for any crimes he "commited or may have commited" afterwards, but what if Nixon was a bit more stubborn, and didn't resign, staying in office for just a precious few more years? What's more, how would 'Nam have been affected?