Military coup. The only way a civil war is successful is if the military are on the side of the people. The most important of which would be the USN and USAF Strategic Forces. A prolonged ground war is only won by sea, air, and nuclear forces. More specifically nuclear forces in the hands of said military who will NOT use them on our own land.

It will present a serious challenge with all the Pentagon purges. But the majority of Flag and Line officers are from West Point, Annapolis, and Maxwell. It's unlikely most side with Trump (for now). The real trick will hinge on the NCOs, as the US Military is predominantly a middle-out force, and senior NCOs hold the bulk of our service members' respect. What they decide to do in the majority will dictate the outcome of a civil war. One NG commander already stated publicly he will order his soldiers to protect protesters from ICE agents. There is a small chance.

Ideally the next time President Trump boards Marine 1 he's taken into custody at a military base with a large Delta, Rangers, or NG presence to subdue USSS agents. With a Federal Judge, Vance, Speaker Johnson, and Grassley in tow. Invoke 25 or Martial Law, and go down the line of succession until someone takes the oath. This is highly unlikely though. A full impeachment is more likely, but a lot of people will need to for die before it will happen.

It's either that or The Man in The High Castle. The American Fourth Reich.