It's insanity. There's no way a guy like this is going to get pardoned, even if Biden had that power. It would absolutely cost the Democrats Wisconsin and be a heavy blow to the Democrats on a national level.
And he has no reason to. Brooks literally plowed through dozens of people and killed six of them in cold blood, then proceeded to make a complete ass of himself on TV and had no respect for the law.
I suspect it will be next to zero.
Wisconsin has shifted into a swing state. Pardoning someone who murdered six people with his car on Christmas, I promise you, will shift Wisconsin red.