Does any party survive attacking it's own base?
The attacks by the Rockefeller wing of the GOP on Reagan and Goldwater proved that as long as they, the rich elitist controlled the part leadership they were willing to withhold funds, advertising and local support from the vocal mavericks rising to national recognition. They knew then and know now that the quiet deals they cut with the Dems will in no way affected their private fortunes nor the movement of the country in concert with the progressives (read Red)
The 1964 Electoral map shows the consequences of Nelson et al behind the curtain actions.
It could well be argued that Johnson benefited from the killing of JFK but the GOP put up no fight.
As a young believer in the Republican Party, I enthusiastically supported Barry Goldwater in 1964 and made my way to the South Orange Arena in New Jersey to participate in a rally for Goldwater where he was to speak. On the way into the facility we observed many Goldwater supporters who could not get in for want of tickets. I'm returning home and turning on the local 11 o'clock news out of New York to be told what I had been seeing, I was stunned to see those supporters of Goldwater converted by the magic of television into opponents of Goldwater protesting his appearance.
I never forgot how easily and deftly the media could lie and in the process simply eviscerate a conservative. It did not help that the the Rockefeller wing of the Republican Party was as least as vicious as Lyndon Johnson in collaborating with the media to abort what might be described as the tea party's spiritual birth.