MADISON, Wis. (AP) -- Unions are facing a make-or-break moment in their campaign to drive Wisconsin's Republican governor from office.

If unions and their Democratic allies prevail in the recall of Gov. Scott Walker, it would send a powerful warning to other politicians who might try to limit union rights. Unions also might find it easier to turn out more voters in November for President Barack Obama in the battleground state.

But a Walker victory would be a major setback for the labor movement.

Unions have experienced mixed results over the past year in trying to beat back efforts in dozens of states to restrict bargaining rights, pass right-to-work laws or limit how unions can collect dues.