My point was that strong principles work great when the country is leaning in your direction. That worked well for the GOP during the period you're talking about, and well for the Democrats from 1932 to 1970.

The "out" party during those periods generally did best when it chose moderates who grudgingly accepted the general ascendance of the other side's principles but sought to moderate them, to do a more competent job of things (Eisenhower, Clinton). The "out" party did not do well when nominating true believers (Goldwater, Mondale).

The Dems spent much of the 70s/80s believing that all they needed to do was play "Happy Days are Here Again" louder and they'd be back in power -- and they could make the same historical argument to support that as you're trying to make.

If you'd like to try the same experiment next decade with "It's Morning in America", be our guest.