By Brendan O'Brien
MILWAUKEE, July 5 (Reuters) - Wisconsin Governor Scott Walker raised an unprecedented $37 million since taking office in 2011, most of it spent to stave off a bid to recall him after he enacted curbs on public sector unions last year, according to a filing on Thursday.
The 44-year-old, first-term governor, who has become a rising national star of the Republican party, spent more than $35 million to defeat Milwaukee Mayor Tom Barrett in the June 5 recall election, according to Walker's campaign finance report filed with the state elections board.
Barrett, a Democrat, was also due to release his campaign finances.
"Overwhelming support from the grassroots was the engine behind Governor Walker's historic victory in June, and that strong support continues in an incredible way," Walker campaign spokesman Tom Evenson said.
Walker trounced Barrett by 8 percentage points, a larger margin of victory than when the two faced off in an election two years ago, and he became the first governor in U.S. history to survive a recall.
The recall victory raised warning flags for President Barack Obama and his fellow Democrats in the first big political test of the 2012 campaign, ahead of the Nov. 6 presidential and congressional elections.
According to the filing, Walker took in $27.7 million since the beginning of the year, during which he went on a nationwide tour giving speeches and raising money to fend off the recall.
He has about $1.6 million in cash in his campaign fund.
Contributions to the Walker campaign far exceeded amounts previously raised by Wisconsin gubernatorial candidates and matched the amount spent by all candidates and interest groups in the 2010 gubernatorial race, the most expensive election in state history.
"Governor Walker matched that himself in this election. It's just insane," said Mike McCabe, executive director of Wisconsin Democracy Campaign, a nonpartisan watchdog group that monitors campaign financing.
Weeks after taking office in January of 2011, Walker angered Democrats and labor groups with his successful drive to limit public workers' rights to collective bargaining. A statewide recall petition drive triggered special elections for Walker, Lieutenant Governor Rebecca Kleefisch and three Republican senators who were eligible to face recall under state law.
The Republicans were largely triumphant in the recall elections, with only Senator Van Wanggaard, who represents Racine County, losing. In defeating Wanggaard, Democrats earned a 17-16 majority in the Senate until the November election, when half of the members are up for re-election. (Editing By Andrew Stern and Paul Simao)