I don't see it as people tolerating the existence of a party, in and of itself. It's more a matter of shifting ideas (which seemed to happen around 1980). I think the culture changed such that more predatory and mercenary behavior was more tolerated, while the Democrats' "bleeding heart liberalism" was being discredited as soft and weak.
Carter was shown as weak during the Iranian crisis, Mondale was weak and also deemed economically inept. The Democrats really didn't do much to dispel this notion, and in fact, they practically confirmed it by the late 1980s when candidate Michael Dukakis wanted to prove how tough he was by showing him riding on a tank.
Democrats have a pattern of electing more decent candidates to manage our national affairs, but might not be tough enough to manage our global affairs. We need a soft touch at home and a pretty hard touch globally.
Clinton was different, although he struck me as Reagan Lite. He seemed a Republican in sheep's clothing, yet so many Democrats flocked to him like he was the greatest thing since JFK.
I think Bill was a good compromise, as he was willing to compromise with republicans on a lot of policies,a nd republicans were willing to compromise with Bill. Gingrich changed all that and was the father of divisive politics that pretty much ruined our federal government since. We can't say 9-11 was an exception because the vote to invade Iraq was based on false intel that was likely the Bush administration. Clinton was savvy and a popular president. Let's be honest, Reagan is Republican Lite today. Would he stand a chance in many conservative parts of America? Hell no. Trump would tear him to shreds for working with democrats.
The Republicans were basically a constant. They hadn't changed much since Eisenhower and Nixon, yet I'm sure they were probably quite amused watching the Democrats dance to their tune.
Really? Eisenhower and Nixon both passed legislation that would not be any platform priority for the GOP today. Eisenhower spent a huge amount of money (of course there was very high tax rates on the very wealthy) on the interstate highway system. Nixon had little pushback on signing Medicaid and expanding social security. In recent years republicans have floated the idea of privatizing SS and eliminating welfare programs. They moved from using high taxes to invest in infrastructure to the idea that cutting taxes will benefit all of society naturally (which is hasn't, it's only helped the wealthy). So I don't see much constant in their approach and policies. Reagan started the whole "government is the problem" attitude, and Gingrich started the whole "we won't cooperate with democrats" attitude. It's been getting more toxic ever since. I suggest it's been democrats who have been the constant, with the understanding that government are people hired to manage our local, state, federal, and global affairs. This is very serious work that requires serious and dedicated people. That Trump became a cult is the antithesis of what politics should be.
I look at Amy Klobuchar, Katie Porter, Sheldon Whitehouse, Sherrod Brown, Elizabeth Warren, etc. as examples of what our elected representatives should be, sober, ethical public servants working for the benefit of Americans, and not being political performers.
It's not so much about the political party as much as it's about a culture shift. George Carlin expressed it when he demonstrated just how far gone the Baby Boomers were. "They went from 'All You Need Is Love' to 'He Who Dies With The Most Toys Wins'." They turned from anti-war peaceniks into warmongers. They turned into Yuppies and NIMBYs.
Those who get caught up in which party is better or worse are missing the point.
This is why I don't blame politicians solely. Vile politicians like Trump, and Greene, and Gaetz, and Desantis, etc. are selected and elected by the voters. I see a lot of complaints by voters who get elected, and it's the voters doing it. It's like someone buying a house they know is falling apart and then blames the house for falling apart.
I still think there needs to be serious consequences to the bad choices voters are making. Was Jan 6 bad enough to serve as a lesson? Was the overturning of Roe enough to serve as a lesson? Was the massive death tool from a bad response to the pandemic enough to serve as a lesson? I don't think so. I still see people complain and want something from politics they are NOT articulating, but also not willing to work for a better government and society. Talk about lazy and entitled society.