What if the left took over without a shot?

There was talk about that during the Cold War.  The idea was that the commies could take over without firing a shot.

After the Cold War ended with an apparent victory, this seemed to go out the window.  But wait a minute.  It seems to be happening right under our noses.

So what would the response be if this were to happen?  Would anything be done in defiance of it?  I am wondering if there is sufficient will and ability to withstand a coup.

There's talk of one of those since the Inauguration.  It seems almost absurd at this point, if evidence, facts, and reason mattered.  But in an argument, force has the better of it.   The truth won't matter.  What will matter is the old calculus of war- who can bring the most force to bear at the critical point.

Who wants it more?  That may be the determining factor.