This afternoon I was doing some research on the 1972 election.
I think had Hubert Humphrey been the Democratic nominee he would have been more successful than George McGovern, especially with labor unions.
I played a 1972 Election with Hubert Humphrey v. Nixon, a rematch of the 1968 campaign. (I also included the AIP candidate John G. Schmitz, who did better here than in reality)
It was still a Nixon victory, but less of a landslide and more of a solid victory.