This means he can be replaced with another Democrat
Graham Platner can be replaced as the Democratic nominee for Senate in Maine if he withdraws from the race by next Monday, and state law would then give the state Democratic Party until July 27 to name a replacement.
The DNC has no real power to tell state parties what to do in a situation like this. In point of fact, their members are largely chosen by the state parties.
I hope you’re right, but forgive me if I don’t hold my breath.