Didn't happen in 1964. LBJ absolutely crushed Goldwater in the general election. I'll let you mumble up the stats on your.
In fact, it also didnt happen for McGovern in 1972, when Nixon smashed the upstart liberal dark horse anti-war senator from South Dakota. And it didnt help that McGovern's first pick for a VP (Eagleton) had to bow out over the revelation that he'd had electroshock therapy to threat depression, something McGovern's team hadn't uncovered when vetting him.
(Side note: If you like American political history and have time to listen to another podcast, I highly recommend Bruce Carlson's "My History Can Beat Up Your Politics".)
P.S. Also applies to Reagan in 1984. In fact, that was probably the year that cemented the notion of 'Reagan Democrats'. Because a LOT of Dems, mostly blue collar folks, voted for Reagan, giving him a clear "mandate".