Madison, Wis. – Wisconsin Republican U.S. Senate candidate Eric Hovde pledged in a new campaign ad Friday to donate his salary to charity if elected, a move that comes as Democrats try to paint the California bank owner and real estate mogul as an out-of-touch multimillionaire.

Hovde has suggested he will spend as much as $20 million of his own money in the race to defeat Democratic U.S. Sen. Tammy Baldwin. The race is one of a few that could determine if Democrats maintain majority control of the Senate.

“I’ve worked hard, been fortunate,” Hovde says in the ad. “I don’t need their special interest money, and I won’t take it.”

Hovde promises to give his entire $174,000 taxpayer-funded salary to a Wisconsin charity every year. His spokesperson, Ben Voelkel, said the exact charities are yet to be determined, but they would not include the Hovde Foundation, a charity run by Hovde’s family.

“I can’t be bought,” Hovde says in the spot, where he promises not to be subject to special interests. Hovde has already said he won’t accept donations from corporate special interests, but he also can’t control how they spend their money in a campaign.

Hovde faces nominal opposition in the August Republican primary. The general election is Nov. 5.

Hovde was born and raised in Wisconsin, but also owns a $7 million estate in Laguna Beach, California, and is CEO of California-based H Bancorp and its primary subsidiary, Sunwest Bank. He is also CEO of Hovde Properties, a Madison-based real estate firm started by his grandfather in 1933.

Hovde has not said if he would divest from his financial holdings if elected.

Hovde’s net worth as of 2012, the last time he ran for Senate, was at least $52 million. Hovde lost in the Republican primary that year to former Gov. Tommy Thompson, who lost to Baldwin.

Hovde and his backers have tried to portray Baldwin, who was first elected to Congress in 1998, as a career politician who has spent too much time in elected office. She spent six years in the state Legislature before being elected to Congress.

Baldwin and Democrats, meanwhile, have painted Hovde as an out-of-touch Californian. Hovde tried to combat that image by submerging himself in a Madison lake in February. He challenged Baldwin to do it and she declined.

“Wisconsin voters will see Eric Hovde for who he is: a megamillionaire, California bank owner who doesn’t share our values and can’t be trusted to fight for us,” Wisconsin Democratic Party spokesperson Arik Wolk said in response to Hovde’s charity pledge.

Hovde’s promise to donate his salary to charity is reminiscent of former Democratic U.S. Sen. Herb Kohl, also a multimillionaire, whose slogan was “Nobody’s Senator but Yours.” Kohl accepted his salary as a senator, which was then $89,500 when he joined in 1989, but returned all of the pay raises to the treasury. Kohl died in December.