MADISON, Wis. — Gov. Scott Walker raised $3.5 million in the first six months of the year as he prepares for seeking re-election in 2014, his campaign reported Monday.

The $3.5 million is even more impressive given that it comes after he brought in just $474,000 the previous six months. The report filed with the Government Accountability Board covers the period through June 30.

That includes the time when Walker introduced, and the Legislature passed, the two-year state budget that cuts income taxes across the board, expands private school vouchers statewide and rejects a federally funded Medicaid expansion. Walker also continued his nationwide travels in the first half of the year, raising money for other Republicans and fueling speculation that he is eyeing a 2016 presidential bid.

"Walker's latest haul is surely buoyed by his frequent trips out of state to campaign for president, but unfortunately for Walker, the people of Wisconsin won't judge him based on his ability to raise money from large corporations and wealthy donors from places like Texas and Iowa," Wisconsin Democratic Party Chairman Mike Tate said in a statement.

"Wisconsin voters will judge Scott Walker on his failure to create jobs and his pursuit of divisive social issues and an extreme tea party agenda at the expense of the economic security of the middle-class," Tate said.

No Democratic candidate has announced they will challenge Walker next year, although former state Commerce Department Secretary Mary Burke is considering it. Without a declared candidacy or campaign committee, Burke wasn't required to file anything Monday.

Burke, a former state Commerce Department secretary and daughter of Trek Bicycle's founder, is expected to tap her personal wealth to help cut into Walker's financial edge if she runs.

A number of other Democrats have been mentioned as potential Walker challengers, including Assembly Minority Leader Peter Barca, state Rep. Cory Mason, Dane County Executive Joe Parisi, Outagamie County Executive Tom Nelson, state Firefighter's Union President Mahlon Mitchell, Winnebago County Executive Mark Harris, and Madison business executive Kevin Conroy.

Any Democrat who gets into the race without their own money to spend will start at a disadvantage.

Walker's report showed he had $2.2 million cash on hand. He spent $2 million through June.

"Gov. Walker has Wisconsin moving forward, and the overwhelming support from the grassroots proves that they want to help him continue to fight for lower taxes, bold reforms, and more jobs," Walker's campaign manager Stephan Thompson said in a prepared statement.

Walker raised nearly $38 million in 2011 and 2012 as he faced recall, with about two-thirds of the money coming from outside Wisconsin. Because he was targeted for recall, Walker wasn't bound by the normal fundraising limits he is under now as he seeks re-election.

Walker set the record for fundraising during his initial 2010 campaign when he brought in $11 million. He shattered that during the recall.

Other reports Monday show Republicans in the state Assembly were outraising Democrats.

The Republican Assembly Campaign Committee raised nearly $223,000 over the period, compared with just $119,000 raised by Democrats.

Assembly Republicans reported $270,000 cash on hand compared with just $73,000 for Assembly Democrats.

The Committee to Elect a Republican Senate said it raised about $153,000 through June and had nearly $124,000 on hand. Senate Democrats had yet to file their report.