The private polls they paid for said that the marx-o-crats would be blamed for a shutdown.
Schumer is also smart enough to understand the fine print on how shutdowns actually work.
Guess what happens to the Federal District Courts during a shut-down?
Almost nobody knows the answer.
It is complicated since they have some operating cash flow from fines (for example)—but at the end of day they would have to beg Bondi for money to stay open—and she would have every right to give them the middle finger and say “no”.