Very dangerous.
The Democrats are going to move farther left. They will become outright pro-socialism, pro-Muslim, pro-social engineering, pro-political tests for everything.
They and their cronies throughout government and media will spend 4 years attacking Trump, worse than you ever saw with Bush.
If they dupe Americans to put them in power again, the USA will become Venezuela of the North.
Or they could tantrum themselves into insignificance, and the vacuum would result in the rise of a more reasonable second major party to rival the GOP. Perhaps it will be called “Libertarian” and it will still be well right of these shriveled, shrunken Democrats.
I suspect you are right. But they will pay the price at the ballot box, provided Trump can stem the illegal tide.