WASHINGTON -- Democrats needed to collect 540,208 signatures to trigger a gubernatorial recall election against Wisconsin Gov. Scott Walker (R). On Tuesday, they announced they had far exceeded that number, collecting more than one million signatures.

Tuesday was the deadline for recall organizers, led by the group United Wisconsin, to turn in their petitions. The number collected is 185 percent of the signatures required to force a recall election. Organizers also collected enough to trigger recalls of the lieutenant governor and four Republican state senators.

The total went far beyond Walker's expectations.

"From what they say, they're probably going to turn in 720,000 today ," Walker said in an interview with right-wing radio host Rush Limbaugh Tuesday afternoon. "That's a lot of signatures, but they've been planning this since late last spring. They've got tons of money from the big government unions in Washington and around the country."

A Walker recall is the next step in a campaign to oust state Republicans who pushed forward controversial budget legislation stripping state employees of their collective bargaining rights . In August, Democrats successfully recalled two Republican state senators from office , but they fell short of the three needed to take control of the chamber.

Republicans plan to challenge the signatures collected by Democrats, and the state Government Accountability Board must certify that of the signatures that were turned in, there are indeed 540,208 valid ones. Democrats had hoped to collect a significantly higher amount in order to buffer against any signatures that may get disqualified. The verification process will take months, and GAB plans to ask a court for more than the allotted 60 days to complete its review process. A recall election -- if it happens -- may not occur until at least June.

There have been only two successful gubernatorial recall elections in history, one against California Gov. Gray Davis in 2003 and one against North Dakota Gov. Lynn Frazier in 1921.

No Democrat has stepped forward yet to announce a challenge to Walker in a potential recall race. Wisconsin Democratic Party Chairman Mike Tate said the party won't put a candidate forward until early 2012 so the recall is viewed as a referendum on Walker and the focus remains on his record.

"The burden is on him here ," Tate told the Associated Press.

While Democrats were announcing the results of their efforts in Wisconsin, Walker was on the East Coast. He has a New York City fundraiser scheduled that costs at least $2,500 per person to attend.

Details from the Wisconsin Democratic Party:

WATCH Wisconsin Democratic Party Chair Mike Tate give a statement on the recall effort: