Former Wisconsin governor and Bush Cabinet secretary Tommy Thompson is laying the groundwork for a run at his state’s open U.S. Senate seat. But as Thompson prepares for his return to politics, the one-time standard bearer for Wisconsin Republicans appears to be facing a conservative backlash.

It was just last year that Thompson was feeling the love from Wisconsin Republicans. The GOP needed a candidate to run against then Democratic U.S. Sen. Russ Feingold. Thompson toyed with the idea for months, promising he’d announce his decision at a tax day Tea Party rally in Madison, Wis. But amid chants of “run, Tommy, run,” Thompson let them down.

“I would love to take this one, but I told my family last night that it’s time for new voices and new faces ladies and gentlemen,” Thompson told the crowd.

Republicans moved on and political unknown Ron Johnson defeated Feingold for the Senate seat. The GOP won big nearly everywhere else.

Flash forward to 2011, when Wisconsin Democratic Sen. Herb Kohl announces he won’t seek re-election in 2012 and Thompson shows interest. This time, he’s not met with the same enthusiasm.

“Tommy Thompson — not what we need in the U.S. Senate,” says an ad by the Club for Growth Action.

The conservative group began running anti-Thompson TV ads preemptively this summer questioning Thompson’s conservative chops though Thompson won four elections as governor, three of them by landslide. Club Spokesman Barney Keller says that was then, this is now.

“If all you care about is having just a Republican — any Republican — in the Senate, then you should vote for Tommy Thompson,” Keller says. “We believe it’s better to have a conservative Republican.”

Keller points to spending increases Thompson oversaw as governor and a letter Thompson co-signed with prominent Democrats calling for a compromise during the federal health care debate.

But Thompson is pushing back, lining up endorsements from old-guard Republicans and hiring prominent Republican consultants. In an interview on Milwaukee talk radio on Monday, he was asked how he responds to contentions he’s no longer in synch with conservatives.

“Very simply. I was the original conservative,” Thompson said.

He points to the welfare reform he pioneered in Wisconsin and the spending increases he vetoed as governor.

Thompson could face Rep. Tammy Baldwin of Wisconsin’s Second Congressional District — the only announced Democratic candidate so far. But first he’ll face a Republican primary challenge – the only question is how big. What appears to be at issue here is old-school conservatism vs. modern conservatism, which often appears to view government itself as the problem.

Copyright 2011 Wisconsin Public Radio. To see more, visit http://wpr.org/.