Challengers lining up to run against Wisconsin Gov. Walker in recall election

Democratic challengers said Tuesday they have more than 1 million signatures in their effort to throw Republican Gov. Scott Walker out of office, but a recall election is not imminent and could still be months away.

Recalling a governor is no easy feat. It has only happened twice in American history. Voters successfully removed California Governor Gray Davis in 2003 and North Dakota Governor Lynn Frazier in 1921.

But Walker opponents successfully took the first step - compiling petitions. Organizers said they turned in more than one million petitions Monday, which is nearly double the amount required and is almost as many signatures as the number of people who voted for Walker.

Now it is in the hands of the Wisconsin Government Accountability Board (GAB) to determine the validity of those signatures. For a recall to proceed, at least 540,208 of those petitions, or one-quarter of the more than 2.1 million people who voted for governor in 2010, must be declared valid. The GAB is supposed to verify the number within 60 days, but the sheer size of the filing and likely challenges from Walker's camp, it could take much longer.

If the board okays the recall election, the primary would be held six weeks after its determination, followed by a general election four weeks later.

At least two candidates have their eye on a recall election.

Kathleen Falk, the former county executive in Dane County, is among the first Democrats out of the gate. She announced her intention to run in a video post on her website. "As your governor, I will make different choices than Scott Walker," she said. Falk served as County Executive from 1997 - 2011 and ran unsuccessfully for governor in 2002.

State Senator Tim Cullen of Janesville announced that he will run before the signatures were even in. On his Facebook page, he promises to stop "the right wing direction that Governor Walker has taken the state."

Another possible challenger is Milwaukee Mayor Tom Barrett, who is expected to address his supporters as early as today about his plans to run. Barrett lost to Walker in the 2010 election 52 percent to 47 percent.

And some Democrats are pressuring former Senator Russ Feingold to run, but Feingold has told supporters he does not want to run himself, a party official told CBS News.

I look forward to working with citizens across Wisconsin to support the Democratic nominee to be our next governor," Feingold wrote on his Facebook page. After losing his bid for reelection in 2010 to Ron Johnson, Feingold founded Progressives United, which focuses on combating "corporate dominance."

Until the board places an official recall election on the calendar, limits on campaign contributions do not kick in, raising the possibility that tens of millions of dollars could be raised and spent in the next several weeks.

Walker's campaign already has political ads on television and radio.

"I expect Wisconsin voters will stand with me and keep moving Wisconsin forward," he said in a prepared statement Tuesday.

Protests against Walker's tenure broke out last year after the first-term governor spearheaded a bill to limit the power of teacher and other public sector unions.

Recall organizers have also submitted petitions to recall Lieutenant Governor Rebecca Kleefisch, Senate Majority Leader Scott Fitzgerald and three Republican members of the state Senate.