If it's obvious that the election is rigged at the time, his team, GOP, and millions of Americans will fight for him and with him. It's a simple question of civilazation, respect of US political system - peaceful transition of power.
It's just him, when he first asked whether he would support other GOP nominies should he lose in primaries, he played similar trick. Later, he relutantly said yes after was further pushed by media and pundits. He just doesn't want to accept the result if he doesn't get the best of it.
赌品看人品。