We knew that organizers had gathered more than enough signatures to force a recall election for Scott Walker, and Walker gave up on challenging the signatures. But it became more official yesterday, as the staff of the Government Accountability Board in Wisconsin completed their review of petition signatures, a prelude to the announcement of election dates.

The staff found 931,053 valid signatures for the recall, less than the 1 million threshold Democrats in Wisconsin claimed, but far more than the 540,000 needed to trigger a recall.

The likely timeline for the recall election is this: primaries for the recall of Walker, Lt. Governor Rebecca Kleefisch and four state Senators will take place on May 8. The general election for the recalls will occur on June 5.

Another poll setting baseline expectations for the Walker recall was released yesterday, and it shows a very tight race.

As for the recall contest of Republican Gov. Scott Walker, 46 percent of Wisconsin voters say they will support him in that race, while 48 percent indicate they’ll vote for the eventual Democratic candidate who will face off against the incumbent governor.

The approval rating for Walker – who sparked a firestorm of criticism in his effort to curb collective-bargaining rights for the state’s public-sector workers – sits at 48 percent approval, 48 percent disapproval. According to the poll, a majority of likely Republican voters say they’re following the recall more closely than the GOP presidential primary race, 51 percent to 37 percent.

I don’t expect those numbers to move much. June 5 will be a long night.

So far, three candidates on the Democratic side have announced that they’re running to replace Walker: Dane County executive Kathleen Falk, State Senator Kathleen Vinehout and Secretary of State Doug LaFollette. Milwaukee Mayor Tom Barrett, who lost to Walker in 2010 in the gubernatorial race, may also run. Barrett would be favored in the primary if he gets in, but Falk leads solidly if he doesn’t.

It’s going to be an expensive race. Walker raised $4.5 million for this recall, boosted by the ability to gather unlimited donations. Outside groups will surely spend millions more.

The race will probably turn on the jobs picture in Wisconsin, where Walker has amassed one of the worst records in the country. The nagging scandal of “Walkergate,” an ongoing investigation into corruption at his Milwaukee County executive office and his gubernatorial campaign, will also be a factor. Finally, the initial spark for the recall, the anti-union bill that Walker forced through amid massive protests, will provide the main source of energy for activists in the race.

With the Presidential primary taking place in Wisconsin next week, both Mitt Romney and Rick Santorum have gone out of their way to praise Walker, in an attempt to curry favor with the conservative base.

UPDATE: At a meeting this morning, the GAB officially triggered the recall, with a May 8 primary and June 5 general election. The filing deadline for candidates is April 10, so Tom Barrett has less than two weeks to make his decision.