Walker was elected in 2010 as part of a national Republican tide. He quickly angered unions and others with aggressive moves that included effectively ending collective-bargaining rights for nearly all public workers.
Petitioners were also submitting about 305,000 more signatures than were needed to trigger a recall election against Lt. Gov. Rebecca Kleefisch and said they also exceeded the number needed to force recall elections of four Republican state senators, including Majority Leader Scott Fitzgerald.
The huge number of signatures against Walker means his supporters would have to successfully challenge about 46 percent of them to stop a recall election, in which Walker would likely run against a yet-to-be-decided Democratic challenger.
"I don't know if it's insurmountable, but it would be extremely difficult," said Joshua Spivak, a recall expert and senior fellow at Wagner College in New York.
During the recall of California Gov. Gray Davis in 2003, petitioners also turned in almost double what was needed and only about 18 percent were tossed, Spivak said.
Wisconsin Democratic Party chairman Mike Tate said that given the number of signatures collected, Walker should not seek delays and instead let the vote proceed.
"Does anyone really honestly believe we're not going to have an election?" Tate said.
In a statement Tuesday, Walker expressed confidence that he would survive a recall and that voters would reward him for balancing a $3.6 billion budget shortfall without laying off state employees or raising taxes.
"I look forward to talking to the people of Wisconsin about my continued promises to control government spending, balance the budget, and hold the line on taxes," he said.
"Instead of going back to the days of billion-dollar budget deficits, double-digit tax increases, and record job loss, I expect Wisconsin voters will stand with me and keep moving Wisconsin forward," Walker said.
Republican Party chairman Brad Courtney issued a statement denouncing what he called a baseless and expensive recall. An election is expected to cost at least $9 million.