Fresh from the only televised leaders' debate, Wynne joined hundreds of Liberal supporters and a dozen candidates in a banquet hall north of Toronto today to make the promise.
She slammed Hudak for vowing that he would resign as premier if he can't meet all his election promises after the Tories form a government, calling it a money-back guarantee.
The Liberal leader says her rival can't govern with a gimmick, then offered her own 20-day guarantee.
Both opposition parties have panned the May 1 budget, raising the possibility that the province could be plunged into another election if the Liberals form another minority government.
Wynne says she can't predict how the Tories and New Democrats would vote on the budget, but suggested that winning the election would serve as an endorsement of the financial plan.