He had the threat of impeachment for misuse of Presidential power before. Now he doesn’t, the House will never be able to bring that against him while in Republican control, and the Senate’s still his. I’m willing to bet we get to see a huge increase in Democrats being impeached across the country. Impeaching Democratic judges, formerly appointed for life. Sure, you’ll need some Democrats on your side, but once everyone is afraid of the gazpacho (/s), more than enough will fall in line. They’re ‘official Presidential acts’ remember, and if you thought they weren’t, their hand selected judges would disagree with you and approve the acts.

Hell, it’s already been mentioned before, all he needs to do is claim a ‘red scare’, then investigate, impeach, and purge the ranks of those that don’t fall in line. And it doesn’t have to be blatant assassination, the people will believe what they’re told.

Edit: uniquely, other than having dissidents randomly fall out windows, Congressmen/women can be expelled without impeachment, with a 2/3rds vote in their respective houses (little ‘h’). So, say a few start throwing themselves out the 5th floor window of hotels… enough remaining will prostrate themselves and vote to expel their peers, same as they would to impeach SCOTUS or federal judges.