I believe it would boil down to who controls the federal military. Drilling down, IF the President has control of the federal military, he/she will determine who wins a civil war. If there has been a coup, then the coup leader(s) or generals independent of any other control - will determine who wins the civil war.
That is laughable!! The standing army (of fags, little girls and LGBTs in their ranks) is only 800,000 on good day and wouldn't stand a chance against a provisional army of millions.
All the comments here are interesting as a thought experiment, but all seem to assume that our side will fight effectively, and that it will be over rather quickly. It might be interesting to continue with the Spanish Civil War analogy.
If it comes—it will be a lot like the last one—with states picking sides and having at it. Blue states follow Democratic Party Coup, Red States follow Trump—It will be Pacific Coast & New England vs. The South and Midwest. Military would shatter. Blue states get help from China, Cuba and North Korea, Red States from Russia and UK. Lots of folks die, cities burned and bombed, Only China wins.