Tommy Thompson close to joining Wisconsin Senate race

After much hand-wringing, Tommy Thompson, the former Wisconsin governor, appears to be jumping into the 2012 race for U.S. Senate.

Thompson, a Republican, is one of the most popular politicians in the state’s history, having served four terms as governor from 1987 to 2001. But his entrance into the fray comes at a time when his party has shifted away from his brand of conservatism.

Specifically, Thompson is on record as a supporter of the health insurance exchanges and other elements of the Democratic healthcare overhaul legislation. As the secretary of Health and Human Services during the George W. Bush administration, he praised the Massachusetts healthcare plan enacted under then-Gov. Mitt Romney. And he supported the massive Medicare drug benefit plan passed during the Bush administration, one that substantially contributed to the current federal budget deficit.

All of that has Thompson viewed with mistrust by “tea party” activists and other fiscal conservatives in Wisconsin. He already faces one challenger in a primary: Mark Neumann, a former congressman who unsuccessfully ran for the GOP gubernatorial nomination last year. Thompson has been working to court tea party voters for months.

Thompson told WTMJ-AM in Milwaukee on Monday that an official announcement of his run to replace retiring Sen. Herb Kohl, a Democrat, would come soon.

“I’ve filed my corporation documents today, which allows me now to build my organization, raise money so I can go out there and tell the story,” Thompson said.

So far, only Rep. Tammy Baldwin has declared a bid to replace Kohl on the Democratic side. Both former Sen. Russ Feingold and Rep. Ron Kind have said they will not run for the seat.

After becoming a focal point in a push by conservatives to limit the collective-bargaining rights of union members, Wisconsin promises to be a fierce battleground in 2012, one that likely will see torrents of money from outside interest groups.