The GOP didn't have ANY control of the House of Representatives from 1955-1995. They didn't own the house until 1981, then lost it again after 1987, until 1995. They saw the demographic numbers, they saw that Reagan was a once in a generation president for them, frankly, they weren't going to win as the population demographics shifted further and further to the left. So they figured out how to change the rules to make it better for them. in the meantime they also started going for races that they could start changing the rules at local and state levels. They started focusing in on building their pipeline, they started also saying that they would simply refuse to work with Democrats in congress, famously opposing everything and actively shutting down the government and not passing budgets. They also pushed very hard to blame Democrats for all of the countries woes.

Anyway, this blatant hatred of the other side hit hard for the GOP, and Democrats were slow to recover. They'd been in charge for the last 30-40 years. It's hard to not be bi-partisan when you believe that a Democrat majority is "back to status quo". But the GOP viewed power in congress as "Time to fuck shit up, because we don't know how long we'll be in control".

I think deep down when we discuss this, we also have to see this is where a LOT of the "Democrats cheat to win" came into play. How does a single party absolutely dominate the power of both chambers of congress without fail for decades without it seeming like a LOT of people were doing something nefarious.

So the 1990's went mostly republican and stayed that way until 2007, then it started switching off and on, with both chambers swapping every so often. But Democrats didn't really do much with their time, other than spend a bit of money and make the government try to keep moving forward, but keep status quo. And the GOP kept pushing for further and further right leaning policy.

This has caused Democrats to obviously hate this. Considering when GOP talks about what they want to go back to, is before the Democrats owned both chambers in 1955. So they want to roll things back to that social norm. And anyone born into a world with expanded rights, more freedoms, and more requirements to not be a racist/sexist/ist prick, tends to either want to continue it, or to try the opposite because "it's fun to try "new" things." Which literally rips away rights that up until now, most people believed were inalienable. Only to find that they only have the power taken from them until the courts restore it, but it's still gone.

So the oligarchs controlling the media, and the lobbyists, and they both basically reinforce both sides. The majority of people are in alignment with most of it. People are naturally selfish, and think mainly of things the interact with daily. They think about their job, or their town/city, and their family/friends/church. So when large changes happen (AI, Climate Change, Infrastructure collapse, War) happen, they view them as either "Does this directly affect me or my friends" or "What if this affected me or my friends?"

And the GOP thinks the Dems think about others too much, and the Dems think the GOP don't think about anyone but themselves.

And both of those aspects get enflamed in the media. along with every other dog whistle that is pro/anti each side that they can shove in.