From what I understand many Republicans voted Dem., as a punishment to the party that didn't build the wall, didn't fix health care and didn't listen when they were giving all three branches. A lot of this falls on the shoulders of Paul Ryan but the coach always takes the blame for an under preforming team. Having punished them I'm afraid they've only made thing worst. As stated Trump will go into bully overload, the Dems., will go into get even mode, and the ship of state will sink with all of us out in the hinterland trying to keep our heads above the water line till help arrives. And remember, the country got here because so many who vote don't have a clue what they're voting for.
The losses were mostly in high-class suburban areas...
Many Republicans who are only Republicans to keep their taxes & WalMart bills low (so, not really pissed about immigration or NAFTA), voted Dem because they don't want a wall built, actually care about the national debt more than immigration, want the President to NOT act like a WWE bad-boy, and don't want to share a political party with 'the help' who fix their leaky faucets.
Trump broke the GOP coalition to win in 2016.
Now the question is can it be put back together again - suburban country-clubbers, rural MAGA-heads, 'pink-purple' soccer moms pissed at Trump's more-or-less bragging about his extramarital sexual exploits, and so on... Before the Dems hand us our asses in 2020