The Republican governor of Wisconsin signed a bill

The Republican governor of Wisconsin signed a bill on Wednesday that will require voters in the state to show photo identification when they go to the polls.

The measure, which Democrats characterize as a voter suppression effort but Republicans defend as a protection against fraud at the polls, will take partial effect just as nine state senators -- including six of Governor Scott Walker's Republican allies -- face recall challenges in mid-July.

Walker called the law a "common sense reform" that would "go a long way to protecting the integrity of elections in Wisconsin."

The law will requires poll workers to immediately begin asking voters to show state-issued IDs before they vote. But voters won't be required to actually produce the IDs until next year. In the meantime, voters who come to the polls without IDs will be handed a flyer outlining the new requirement.