I think that the MSM have been going increasingly partisan for most of my lifetime, from covering up JFK's whoring to being adversarial with Nixon and Reagan to the Mapes/Blather phony memo October-Surprise fail to going utterly wacky-partisan with Trump. With much more @#$% in between through the decades.
I was a little young for Nixon in '60 to understand national politics and problems, but I remember the '64 campaign and Goldwater getting killed daily by the media and even in various entertainment venues.
Goldwater hated blacks and minorities and was itching to start a nuclear war as soon as he was inaugurated the national media proclaimed.
Some of the phrases from his campaign were questionable, but the one the media latched on to was the "extremism in the defense of liberty is no vice."
That came from Goldwater's speechwriter Pat Buchanan. Liberals interpreted that to mean Goldwater couldn't wait to press the nuclear button.
And Goldwater's opposition to the '64 civil rights bill hurt him badly with blacks. And after JFK's assassination, it would have been pretty tough for any Pubbie to win in '64. National sympathy was with the Dems and maybe the most conniving, deceitful Dem pol ever, LBJ.
Getting stabbed in the back by Rockefeller Republicans didn't help much either.
When George Wallace said there wasn't a dime's worth of difference between the Dems and Republicans, he was probably talking about the Rockefeller Republicans who ran things in the Republican Party for many decades.
The reality was Goldwater was probably the sanest politician in Washington and was actually pro civil rights. He just thought the '64 bill went too far. It did. We're still paying dearly for some of the provisions in the bill.