Inspired by the thread I made on the McGovern-Carter ticket, and how that failed to make much difference besides the obvious.
Anyway, the only idea in this challenge is to get McGovern in office. You can change his election strategy in 1972, or perhaps have him run in a different year (1976, 1980, 1984, 1988, 1992...) or have him as a vice presidential running mate to a different candidate.