I've been reading William Patterson's biography of Heinlein, which I'll talk about in an upcoming "What am I reading" post; but I've just gotten to the section where Heinlein campaigns for Barry Goldwater, apparently because Lyndon Johnson was an anathema to Heinlien's new political views.
I'm not precisely a fan of Johnson, though I'll note he did sign the Civil Rights Act in 1964, at great political cost to him due to angering the Southern Republicans (formerly the Dixiecrat Democrats, these legislators had switched parties in outrage over the support of the Democratic party for civil rights).
Goldwater himself was pro-civil rights, but he was also very much a Republican. The Southern Republicans backed him, despite his pro-civil-rights record, mainly due to his opposition to FDR's New Deal, and his outspoken determination to do whatever necessary to take down the USSR -- and whatever necessary included nuclear attacks. Famously, he said in his speech accepting the nomination, "I would remind you that extremism in the defense of liberty is no vice. And let me remind you also that moderation in the pursuit of justice is no virtue."
I can see why Heinlein supported him, in other words: like many in those days, he was terrified that the USSR would attack the US with nuclear weapons. Many, many people then believed such a war would be survivable (spoilers: it would not), but Heinlien was convinced that the Russians would then invade and occupy the country. (What country? The nuclear slag that had been a country?) He was making plans, in fact, to become a guerilla fighter in this struggle against the Russian invaders.
Goldwater's stated willingness to use nuclear weapons against the Soviet Union seemed, to Heinlein and some others, precisely the sort of saber-rattling the US needed to keep the USSR in check. To most of the US at that point in history, it seemed unhinged. We'd just come close to nuclear war in the Cuban Missle Crisis; no one wanted a repeat.
I have a personal memory of the Goldwater/Johnson campaign, just a short snippet. I would have been three years old, but I remember riding in the backseat of our car (a Dodge Lancer) listening to my father tease my mother, insisting he was going to vote for Goldwater, and her scoffing that he wasn't going to do any such thing.
Goldwater -- and this is another reason Heinlein probably supported him -- called for massive cuts in social spending, as well as shifting government programs to the private sector. The TVA, for instance, he wanted taken over by a private business.
But in most respects, he was what we would call a center-right liberal today: he opposed the war in Vietnam, for instance; he repudiated the KKK when they came out in support of him; he insisted on desegregating the Senate cafeteria, bringing his African American assistant in to dine with him.
But he also endorsing using nuclear weapons in Vietnam, opposed legeslatin to outlaw poll taxes, and argued for cutting government spending to the bone. He voted against the Civil Rights Act, because he didn't believe the Federal government should intervene in how states governed themselves (the "states rights"today's Republicans believe in, so long as the states are doing things they agree with); and he argued that government intervention in things like poverty were creating a "moral decay" which would destroy the country.
Goldwater was defeated in a landslide: in 1964, the American public repudiated and were revulsed by his center-right platform.
Sadly, his more extreme views lived on, and both infected and created the current American conservative movement.
Our nation has indeed changed since 1964 -- not to its benefit. In 1964, the American people rejected Goldwater as too extreme, and far too removed from factual reality. In 2016, the American people elected Donald Trump, whose entire unhinged brand was an extremism entirely removed from factual reality.
That's not a change for the better, to put it mildly.
(The famous anti-Goldwater commercial: