He's already putting up a huge fuss and he hasn't even lost yet.
He's clearly one of the world's sorest losers -- allowing and encouraging crowds to chant "lock her/him up!" for his political opponents, calling fraud, touting conspiracy theories, etc, are not the mark of a man humble in defeat. But what bothers me is that he really needn't be like this. It's likely to be a defeat, but a defeat far less spectacular than many had expected/hoped for. And it's a defeat that sets the tone for four years of stalemate and arguing and continued infighting, in which very little will be done. It seems that the Lower House is going to the Democrats, but by less than previously; the Republicans will retain control of the Senate; and they've already secured the Supreme Court and many other judicial offices.
If Trump wants to run again in 2024, and he probably will, I'd almost be tempted to call him favourite.