Harris doesn't need to "attempt it", she somehow became the Democratic choice without a single vote for her, replacing the man who said it'd be ridiculous after all the millions of votes he got
Like it or not (I don't!), primaries are internal functions of membership organizations. The law has found this again and again. In these contests, it is the party delegates who are given the right to choose the party nominee.
And then...
Directs the military to strike on [target] and the military says "Not my Commander" and no strike is carried out.
There is no Coup unless the powers are transferred.
It cannot happen.