with the substitution of Iran (or the Middle East at large) for Vietnam
Ford's granting of a pardon to his predecessor, Richard Nixon, along with soaring inflation caused by the 1973 oil crisis, created a tough environment for the Republican Party.
https://en.wikipedia.org/wiki/1974_United_States_elections
https://en.wikipedia.org/wiki/1970s_energy_crisis#Arab-Israeli_conflict
I'm sure Vietnam played a part, but it was also corruption and high gas prices caused by US involvement in the Arab-Israeli conflict, same as now. History repeats itself.