Thats a great question and a number of answers. Some were saying that the Democrat leadership new better that to let Biden near a debate stage so they gave Trump a deal he couldn’t accept because there were so many rules that favored Biden but Trump turned the tables on them as accepted. That put the Dems in a pickle and the had to go through with the debate.
Or, Maybe they wanted to dump him so they wanted to make him look so bad that they had a reason to replace him with somebody else. But now the problem is how do they get rid of Kamala; that’s going to be fun to watch.
Out of the Cave 