Wealthy businessman Eric Hovde has entered Wisconsin's already-crowded GOP Senate primary field, creating more chaos in an already-unstable field.

The field already includes former Wisconsin Gov. Tommy Thompson (R), former Rep. Mark Neumann (R-Wis.), and Wisconsin state Assembly Speaker Jeff Fitzgerald (R).

Hovde's entrance adds further uncertainty to the race: It's unclear whether he'll help the former governor by further dividing the anti-Thompson vote or find a middle path to the nomination by spending heavily to win over conservatives unhappy with the field.

A Madison native who has lived for years in the Washington area, Hovde said when he was first mulling a bid that he might spend as much as $10 million on the campaign. He's also a polished speaker who has regularly appeared on cable news shows to discuss the economy. 

"Washington is full of career politicians who are beholden to the special interests that finance their campaigns," Hovde said in a statement announcing his candidacy. "We need citizen legislators who have spent time in the private sector and who have the skills to put our economy back on track."

A Hovde campaign source said he'd run as the only non-politician in the race, although running as a Washington outsider might be tricky for a man who's lived in the D.C. suburbs for years.

Thompson has come under fire from various conservative groups for working with former Sen. Tom Daschle (D-S.D.) on a bipartisan framework for health care reform, although he denounced the bill Democrats pushed through Congress and President Obama signed. He's also been criticized by conservatives for working closely with state employee unions while governor, a hot-button issue given now-Gov. Scott Walker's (R) battle with those unions.

Neumann has the backing of many D.C.-based conservative groups including Sen. Jim DeMint's (R-S.C.) Senate Conservatives Fund, the Club for Growth and Freedomworks. But some Wisconsin conservatives are still angry at him for his testy 2010 gubernatorial primary run against Walker. Recent polls have shown him and Fitzgerald, a close Walker ally, splitting the conservative vote and giving Thompson the edge in the race.

The four Republicans are vying to replace retiring Sen. Herb Kohl (D-Wis.). Rep. Tammy Baldwin (D-Wis.) is all but certain to be the Democratic nominee.