Confirming yet another Supreme Court Justice would completely DE spirit most if not all the moderate democrats.
The truth is if that happens it will probably fracture the Democrat party permanently the extreme left will go extremely berserk and the moderates will start to fade.
You raise an interesting question. Would pre-election confirmation of POTUS’s pick increase or decrease Dem turnout? One can make an argument for both scenarios. But I tend to think it will depress turnout more than increase it. With one more conservative on the court, many demoralized Dems may view the Supreme Court as a dead issue that they have already lost.