WASHINGTON -- Wisconsin Gov. Scott Walker (R) made headlines on Monday when he announced that he had pulled in an unprecedented $13.2 million in three months to fend off a Democratic attempt to recall him from office. His campaign said "grassroots donors" had boosted his haul, with 76.4 percent of the contributions coming from donations totalling $50 or less.

But a closer analysis of his contributions by The Huffington Post shows that Walker was aided by individuals outside the Badger State, as well as by deep-pocketed donors who are fueling the conservative super PACs that have become major players in national races. Two-thirds of Walker's donations came from outside of Wisconsin, and $3.57 million came from individuals giving $10,000 or more.

Walker's Democratic challengers didn't even come close to matching his fundraising. In the most recent three-month reporting period, Milwaukee Mayor Tom Barrett raised $830,000, while the other frontrunner on the Democratic side, former Dane County Executive Kathleen Falk, brought in $1 million. The other two Democratic candidates, Secretary of State Doug La Follette and State Sen. Kathleen Vinehout, each raised less than $200,000.

Walker, however, was playing by different rules. Under Wisconsin state election law, contributors can give a maximum of $10,000 to a gubernatorial candidate. But the targets of recalls can raise unlimited funds from when the first recall petition is filed until the processing of the signatures is completed. Therefore, Walker was able to raise contributions of unlimited amounts until March 30, while Democrats were gathering and processing signatures to trigger the recall.

Democrats, meanwhile, were forced to abide by the stricter contribution limits during the whole reporting period, since they were not the target of the recall.

Walker raised $3.57 million in donations over $10,000. Nearly half of that -- $1.67 million -- came from 37 Wisconsin donors, including a $500,000 donation from Diane Hendricks, the billionaire head of the roofing company ABC Supply. Her donation was the single largest contribution to a gubernatorial candidate in Wisconsin history. The second biggest in-state donor to Walker's recall campaign in the pre-primary report was the Republican Party of Wisconsin, with three contributions totaling $369,516.

Walker's list of $10,000-plus out-of-state donors, who gave a total of $1.89 million, consists of some of the biggest donors in the Republican Party, including some big donors to prominent super PACs.

Casino billionaire Sheldon Adelson, who gave $21.5 million to a super PAC backing Newt Gingrich's presidential candidacy, contributed $250,000 to Walker's recall fund. The billionaire founder of the hedge fund Moore Capital Management Louis Bacon kicked in $100,000 to Walker's cause after giving $500,000 to the super PAC supporting presumptive Republican presidential nominee Mitt Romney. Another pro-Romney super PAC donor, Missouri roofing company head David Humphreys, gave $10,000 to Walker. One backer of Rick Santorum's presidential bid, John Templeton of Pennsylvania, gave $10,000 to Walker's campaign.

Other super PAC donors giving to Walker Virginia James, Richard Uihlein and John W. Childs, donors to conservative groups Club for Growth and FreedomWorks, and J. Joe Ricketts, one of the primary funders of the anti-incumbent Campaign for Primary Accountability.

Walker has frequently criticized the influence of unions and out-of-state money coming into the state to help the Democrats in the recall process. Last year, for example, he slammed the "big government union money coming in from Washington."

But Walker is certainly no stranger to out-of-state funds. In fact, the vast majority of money he raised from mid-January to mid-April -- $8.37 million -- came from donors outside of Wisconsin. In-state donors only accounted for $4.36 million, or one-third of his pre-primary total.

Small donors giving less than $200 to Walker's campaign, rather than large donors contributing more than $10,000, were the biggest drivers of out-of state donations. Of the total $5 million Walker received in contributions from these small-dollar donors, 70 percent -- or $3.46 million -- came from out-of-state donors, likely signifying the importance that grassroots Republicans nationwide are placing on Walker's success.

The Walker campaign did not return a request for comment on Tuesday, but in a statement on Monday, campaign spokeswoman Ciara Matthews said, "We continue to see strong grassroots support for Governor Walker, his bold reforms, and his plans for moving Wisconsin forward. Because of the overwhelming support for the Governor, we can continue to speak to voters about how Governor Walker plans to move Wisconsin forward while his Democrat opponents plan to take Wisconsin backwards to higher taxes, record job loss, and massive deficits."

In January, Walker told The Huffington Post that he needed to raise so much money from out-of-state donors to match the spending by the unions. The governor was in Washington, D.C. at the time for a speech at a conservative think tank and a meeting with Republican donors at the Capitol Hill Club.

But so far, Democrats aren't even coming close to matching Walker. An independent group affiliated with labor unions backing Falk raised $4.5 million in the last fundraising period.

Walker has raised more than $25 million since January 2011, and now has $4.9 million cash on hand. He has spent more than $11 million since mid-January. WisPolitics reports that $60,000 of Walker's pre-primary money was transferred to his legal defense fund, which was set up to deal with a "John Doe" investigation of Walker's time as Milwaukee county executive that has already ensnared several of his former staffers.

Democrats choose their nominee in a primary election on May 8. The general election is set for June 5. In addition to Walker, the lieutenant governor and four state senators are facing recall challenges.