The proposed scenario doesn't have to happen.
As it stands right now you have two huge names in media telling their millions of followers that Biden is a bumbling retard and doesn't have the balls to step up.
And Trump's re-tweeting it.
That's massively damaging to an already damaged Biden/Harris ticket.
Just like when he offers to send in federal "troops" to help fix civil unrest in Lefty cities. He gets to claim he cares about these schitholes, knowing they would rather die than take his help with anything. He doesn't actually have to do anything, take credit and bash the incompetent local Liberals at the same time.
