While mostly true they were doing it because doing otherwise would cost them votes, it didn't matter in the long run. Republicans knew then it was in the best interest of the presidency and the country for Nixon to resign but even if they only acted out of self interest, they acted. Just like Ford knew it was in the best interests of the country for him to prevent a useless prosecution of Nixon by pardoning him, even though he knew it would make his election in his own right very difficult.
Its for this very reason I want progressives and Democrats to quit focusing on every social demographic like the only way we can save the LGBT community is to make a point of pointing out how they are the only saviors of the LGBT community. I don't care how Clinton could have won, or how Democrats might win the House or Senate in 2018, I just want them to win. Focus on the one item that will unite the working poor, the working class and the middle class: Jobs and the economic direction and future. It is the only realistic path to victory.