How can they? They HAVE NO answer! And thus the big lie of this entire recall. The only way to "undo" what Walker has done is to raise taxes, massively. Falk says she won't sign any budget that doesn't undo the collective bargaining changes. Barrett says he'd call a session, which would lead to utter chaos in Madison if Dems hold one house and Republicans the other, which could happen if Barrett wins the recall.
But no matter how you get there, "there" is the land of dramatic tax increases to restore what public employee unions want back. The not so secret dirty little secret.