I heartily agree with your point that outrage is the most powerful factor at work in modern American politics. But my own perception is that the outrage factor has been dominant in Republican politics since the 1990s, and now Mr. Trump has triggered enormous amounts of outrage venom among Democrats. Thus, all Republican successes for the last 20 years have been built on stoking fear and outrage; they’ve pretty much played that card as far as it can take them. Mr. Trump pushed fear and outrage to the most extreme limits, with his stream of tweets warning about Islamic terrorists, Mexican rapists, Chinese job-stealers, Iranian nukes, and on and on. But he’s scraping the bottom of the barrel on fear and outrage; there just aren’t any more Republican voters to be outraged.
On the other hand, Democrats, especially the young, have been fairly laid-back about politics for the last 20 years. Trump was more than a wake-up call: he was a kick in the groin. I know a great many liberals who are genuinely fearful that Mr. Trump is another Hitler. Yes, their fears are overblown, but Republicans have been running on the fuel of overblown fears for 20 years now and now we’re seeing overblown fears among the Democrats.
Especially important is the youth movement. The kids have been asleep for years now, but climate change has gotten them off their butts and they are genuinely terrified for their future. Moreover, we have lots of events to confirm their worst fears. A tornado killed 23 people in Alabama on Sunday! OMG! In the larger scheme, 23 dead is no big deal, but death and destruction is the red meat of all news media; the heavy coverage the tornados got has nothing to do with politics and everything to do with drama. We had all those extreme cold weather events, which push their fears even further. In a few months we’ll start seeing the wildfires, and more headlines to keep the kids awake and night. Meanwhile, we’ll be seeing continuing stories of scientific studies with dire implications, ice melts in Antarctica and Greenland, sea level rise, floods in the Sahara Desert, and droughts in Rutabagistan. 😛
You should check the polling results on the Kavanaugh hearings. The majority of Americans did not believe Mr. Kavanaugh, and disapproved of his confirmation. Yes, the accusations against Mr. Kavanaugh energized Trump’s supporters, but Mr. Kavanaugh’s denials infuriated many more people, especially women. Women are drifting away from the Republican Party. See also this poll from Pew.
The Republican Party is strongest with white voters. If its future base consists primarily of white men, then it doesn’t have much of a future.