What is it with Wisconsin? Just in the past year we've had the defeat of Russ Feingold, the war over Scott Walker and now...the tarring of Tommy Thompson. It's gone mostly unnoticed amidst all the drama of the Republican presidential primary, but the biggest congressional primary showdown -- 2012's answer to the 2010 battles that produced Sharron Angle, Christine O'Donnell and Ken Buck, among others -- is shaping up over the right to take on Iraq war veteran Tammy Baldwin for the Senate seat being vacated by Democrat Herb Kohl. Thompson, the former governor and health secretary under George W. Bush, will face Mark Neumann, a former congressman with impeccable conservative credentials: his own party kicked him off the appropriations committee in 1995 for voting against a spending bill and he's no slouch on social conservative issues (choice quote, from 1996: "If I was elected God for a day, homosexuality wouldn't be permitted, but nobody's electing me God.") Neumann left Congress after narrowly losing his challenge of Feingold in 1998; last year, he ran in the gubernatorial primary to Walker's right (no easy feat) and lost.

As if this wasn't enough to get conservatives excited, they really have their knives out for Tommy Thompson. This might seem hard to figure to anyone who recalls that it was Thompson, along with his Michigan counterpart John Engler, who got the ball rolling on welfare reform in the 1990s. But to conservatives, this success actually edges into their overriding concern about Thompson, that he's at heart a reform-minded pragmatist, with a bit too much of the old Wisconsin progressive tendency to be trusted. This is embodied by his chief offense: having spoken out in favor of the Affordable Care Act. In the fall of 2009, when conservative ire against the legislation was at its peak, Thompson put out a rather out-of-nowhere statement with Dick Gephardt praising the bill that had emerged from the Senate Finance Committee (which was more modest than what the House was considering at the time.) The statement called the bill "another important step toward achieving the goal of health care reform this year. It moves us down the path of providing affordable high-quality health care for all and expanding coverage for millions."

President Obama eagerly touted this "bipartisan" support and Thompson's standing with the right was shot for good. Just in the past day, I received an e-mail alert from Jim DeMint, leader of the Senate conservatives, warning about Thompson and seeking support for Neumann, and from the Club for Growth thundering about further evidence of Thompson's support for Obamacare, as if any more proof was needed -- revelations that Thompson in 2009 and 2010 served on the board of a progressive, labor-affiliated group called America's Agenda. This will be a fun race to watch. More importantly, though, it's another reminder that the fight over Obamacare next year could be far more nuanced than one might have expected just a year ago. Both of the two leading candidates for the Republican presidential nomination are seriously compromised in their opposition to the law by their past support of many of its tenets, and one of the highest-profile GOP Senate primaries will feature a well-funded former Bush administration official fully on the record as supporting the law.

A final thought, getting back to my opening question: why all this excitement in Wisconsin? I suspect what we're seeing is a manifestation of the remarkable mix of political traditions that has long defined that state, with on the one hand, its deep progressive, even socialist, roots going back to the transplanted Yankees and northern European immigrants who settled it; and on the other hand, its nearly as well-established strain of deep conservatism that has at moments strayed into nativism and demagoguery, most notably in the person of Joe McCarthy. Jason DeParle's superb history of welfare reform, "American Dream," set in Milwaukee, notes another feature of the state that surely helps explain its polarized politics: the Great Migration got to Wisconsin later than anywhere else. While Southern blacks were pouring into othern northern cities at midcentury, Milwaukee was still overwhelmingly white in the 1950s; it was only later, in the 1970s and 1980s, that a second wave of migration carried African-Americans to Milwaukee, mostly from Chicago. This means that metro Milwaukee is further behind in the cycle one has seen in other cities, where, after an initial white flight, the suburbs are now themselves growing increasingly diverse and Democratic. Milwaukee hasn't moved as far from its initial white flight phase, and its suburbs -- not all, but most -- remain a hotbed of Republican votes (and, not incidentally, home to some virulently conservative talk show radio shows.) Thus can the same state give one both Russ Feingold, Paul Ryan and Scott Walker, and now Tommy Thompson vs. Mark Neumann. Expect to read plenty more about Wisconsin in this space in the year to come.