Wisconsin Republican Terrence Wall, a real estate developer and a frequent donor to GOP candidates, is challenging Democratic Sen. Russ Feingold.

Wall filed a statement of candidacy Oct. 21 and a statement of organization with the Senate’s public records office. Those documents allow him to begin raising money for a campaign against Feingold, who is seeking a fourth six-year term. Wall’s campaign Web site is not yet active.

Wall, who comments on economic issues on his company’s Web site, has donated to numerous Republican candidates and committees inside and outside Wisconsin. He donated to the 2008 presidential candidacy of former New York City mayor Rudy Giuliani, then gave money to Arizona Sen. John McCain after he secured the Republican nomination.