Humphrey wins election in 1968 over Nixon, picking up battlegrounds like Missouri, Illinois, Ohio, and New Jersey, just barely giving him the edge needed to pass 270 votes. (Alternatively, we could say that nobody got the 270 electoral votes and the House, which was controlled by the Democrats, chose Humphrey by default.)
He continues the programs of Johnson's Great Society while gradually pulling the troops out of Vietnam before the election begins. He's re-nominated despite opposition by George McGovern, and Muskie gets the Vice Presidential nomination again.
Reagan gets the Republican nomination (which he had sought in 1968) and Bob Dole of Kansas gets the V.P. nomination. Who would you vote for?
Let's see some maps, too!