Political comeback?  That’s what Wisconsin media are calling Tommy Thompson’s win in yesterday’s primary, which turned out to be rather easy after a tough campaign:

Former Gov. Tommy Thompson took a major step in his political comeback Tuesday, winning a four-way Republican primary for an open U.S. Senate seat and setting up a sure-to-be nationally showcased November battle with Democrat Tammy Baldwin.

The Thompson-Baldwin contest will feature two candidates who are ideological opposites. On top of that, if the 50-year-old Baldwin prevails she would become the first openly gay member of the Senate.

Thompson declared victory shortly before 11 p.m., telling cheering supporters gathered at hotel in this Milwaukee suburb that “Wisconsin is on a roll” — a reference to the political star power of Republican Gov. Scott Walker and the newly selected GOP vice presidential choice, U.S. Rep. Paul Ryan of Janesville.

With more than 90 percent of the vote counted, Thompson led his nearest rival by some 20,000 votes.

Thompson had to run against a trio of tough primary opponents, who more or less split whatever coalition might have defeated the more establishment winner.  Tea Party grassroots went with either self-funder Eric Hovde and Club for Growth favorite Mark Neumann, who had represented Wisconsin in Congress before, as a member of the House rather than the Senate.  On top of that, Assembly Speaker Jeff Fitzgerald also had his hat in the ring, and his close ties to Scott Walker and his leadership in the Fleebagger crisis made him a formidable opponent.

Thompson now has to take on Tammy Baldwin, who might be even more doctrinaire liberal than former Senator Russ Feingold.  Baldwin wants to run for the open Senate seat left by Democrat Herb Kohl’s retirement by adopting the union playbook.  The NRSC has already begun painting her to the left of Barack Obama, and Baldwin has responded by attacking Republicans as the party of wealthy interests rather than the people.   That used to sell in Wisconsin, before the unions tried to undo an election and take over the state government.  This year, that attack simply doesn’t work, even when the unions spent millions to demonize Scott Walker after the public-employee union reforms took effect.

It will probably work even less in November against Thompson.  The former governor and Secretary of HHS has too long a record on the center-right to be painted as an extremist, and Thompson will benefit from Walker’s GOTV organization and the sudden competitiveness of Mitt Romney against Obama in Wisconsin.  If Thompson wins, the GOP takeover of Wisconsin will be all but complete within two years — a stunning turnaround for the cradle of Midwestern populism.