President Obama won't dare go to Wisconsin himself to campaign for Barrett as the move is deemed too risky for the fragile incumbent, so a last-minute Tweet of support will have to suffice:

Instead the administration dispatched Bill Clinton, Jesse Jackson, and Debbie Wasserman-Schultz to the state in Obama's place. 

Democrats are hedging their bets and anticipating some sort of loss tomorrow, thus the move to protect Obama the candidate from any association with loss by avoiding the state altogether. How much of a loss will depend on voters tomorrow.