Trump is a result, not the cause.
It is conservatives who rejected any compromise or cooperation with "the enemy", and punished transgressors.
In the 70s and 80s they targeted Rockefeller Republicans to unseat them and drive them out of any position of power, all because the R Rs stood in the way of their complete-deregulation and "damn the deficits, full tax cuts ahead" priorities. They sought out what hot buttons to push to get people single-issue voting, the better to beak up Democratic voting blocs.
In the 90s they faced their worst nightmare: a charismatic "pro-business" Democrat from a southern state, one who was ok with the death penalty and cutting back on welfare. All the usual Republican campaign rhetoric against Democrats were wet noodles against a guy like that. A guy like that could peel off enough support that all the conservatives' pet projects would be stymied for years or completely undone. A guy who wouldn't be giving conservative partisans lifetime judicial appointments.
So they went full hot button: What's your nightmare? Look! Bill and Hillary Clinton are IT! What's your pet peeve? Bill and Hillary Clinton do it! What have you spent years grinding an ax about? Bill and Hillary Clinton are its living embodiment! They ran against Draft-Dodgin' Dope-Smokin' Jazz-Playin' Slick-Talkin' Citizenship-Renouncin' Hippy Bill and Manhatin' Harpy From Hell Hillary. Newt Gingrich enshrined that tactic, and changed the House rules to further discourage "fraternizing" with Enemy colleagues.
In the end Newt stepped down as Speaker because the Salome Caucus he'd built was going to boot him for failing to deliver the head of Bill the Clinton to them on a silver platter.
2008 rolls around, and they take that playbook they built up in the 90s and use it as a starting point, with extra racism on top. Total Opposition. Screw economic recovery, we have to make sure this Chicago guy is a one-term president. No cooperation.
They voted against their own bills when Obama said "Ok, if that's what it takes to get it done, we'll do it your way" because they could not be seen shaking hands and cooperating with the new boogeyman. Anything less would have the Salome Caucus putting them on the silver platter list.
Conservatives treated all internal opposition as slackers, apostates, and fifth columnists. And they've done so for decades. They turned the Party of Lincoln into the Party of Ahab, and anyone who gets in the way of the hunt for the White Whale...
... the sum of all the general rage and hate felt by his whole race from Adam down; and then, as if his chest had been a mortar, he burst his hot heart’s shell upon it.
They built that.
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