Biden’s team argues: “The rules won’t allow Biden to be replaced.”

That’s not right.

It is true that if Biden does not withdraw from the race on his own, release his delegates and open up the convention, there is no way that he can be denied the nomination, short of death or disability. If he does take himself out of the running, however, the Democratic National Committee has the authority to do whatever is necessary to fill the vacancy under its existing rules.