A revolution or an insurrection is likely to lead to a civil war. A civil war is a war, and will probably be an especially horrible example of a generally horrible business. So we can look to general principles of “just war” theory, one of which is that a just war should be a last resort.
I very sincerely hope–and am even cautiously optimistic–that the elections in November will remove Trump from power, perhaps with at least some (maybe many) of his most reckless and feckless enablers in Congress.
If elections were no longer an option–if they were outright cancelled (including being “postponed” “for the duration of the emergency”) or if the process were so completely corrupted as to be meaningless (that is, even if most people in reality voted against “the regime”, it would still be reported that the Glorious Leader won re-election by a landslide)–then it would be time to go beyond the ordinary political process. Even then, there are things between “voting” (and “normal” demonstrations) and armed revolution–truly enormous mass demonstrations (hundreds of thousands of people taking to the streets of the capital city); a “general strike” which shuts down all economic activity; and so forth. Think of the peaceful “people power” revolutions like those seen in the Eastern Bloc in 1989.
But if some hypothetical American “regime” (having already cancelled or stolen elections) responded to such a bloodless attempted revolution like the Chinese regime did that same year in Tiananmen Square, then it would be time to start the very, very ugly business of resisting such a repressive and bloody-handed regime by force.
There is also, of course, the very difficult question of a government which is repressive, but maybe only to a minority of the population, and which actually wins the election. Again, just war theory will argue for war (armed violence) as a last resort, for proportionality, and also that war should only be attempted if there is a reasonable probability of success. In terms of their systematic deprivation of civil and political rights (which, after Reconstruction, had been explicitly guaranteed to them by the Constitution) African-Americans would have been morally quite justified in resorting to arms–except that in the end, they were able to achieve the overthrow of the Jim Crow system by mostly peaceful means, whereas an African-American armed insurrection would likely have been crushed by the more numerous and better equipped majority of the country. So, an armed insurrection against Jim Crow would not have been a “last resort” and it would not have had much likelihood of success.
The “probability of success” criterion would not, I think, apply to a minority which was facing actual genocide–in that case, even if the cause is hopeless, I would say you might as well take as many of the bastards with you as you can.