After a flurry of speculation in the past 24 hours, Paul Ryan has decided to stay in the House rather than run for the Senate seat vacated by Herb Kohl’s retirement, reports Major Garrett at the National Journal.  Ryan will announce his decision later today, which will leave the field open for former governor Tommy Thompson:

Rep. Paul Ryan is staying in the House, and won’t run for the U.S. Senate, two well-placed GOP sources tell National Journal.

Ryan began informing close friends of his decision Tuesday. Three GOP sources tell National Journalas soon as Ryan officially announces he won’t run for the Senate, former Wisconsin GOP Gov. Tommy Thompson, is expected to announce his candidacy for the Senate seat being vacated by Democratic Sen. Herb Kohl, who recently announced he was retiring.

Earlier today, Politico reported on Thompson’s decision to toss his hat in the ring:

Tommy Thompson, the Republican former Wisconsin governor and George W. Bush’s first secretary of Health and Human Services, has told friends he plans to run for the open Senate seat in Wisconsin, according to top Wisconsin sources. …

Thompson would give Republicans a popular former two-term governor to seriously challenge for this toss-up seat, which could prove the difference as Senate Democrats struggle to defend their majority with now eight retirements.

Thompson tried an ill-advised presidential bid in 2007, dropping out after a couple of painful debate performances.  He’ll do better at home, where Thompson has found repeated political success.  Thompson won state-wide office four times as governor, even when Upper Midwestern progressivism was still in vogue.  (Politico lists him as a two-term governor, but Thompson was governor from 1987 to 2001, resigning to take a position on George W. Bush’s presidential Cabinet.)  He beat an incumbent Democrat by 5 points in his first attempt, then attracted no less than 58% of the popular vote in the next three elections.

Steve Eggleston wonders if this will be for real in the Green Room, recalling Thompson’s Hamlet performance in 2010:

On this morning’s show, WISN-AM’s Jay Weber mentioned a pair of items that suggest that this time, Thompson’s campaign is real – Thompson reportedly regrets not running against then-Senator Russ Feingold in 2010 despite polls that suggested that he would beat Feingold. Further, Republican Party of Wisconsin executive director Mark Jefferson reportedly told Thompson that if he were to run this time, he would need to really run, and announce early.

Assuming Thompson runs, he will be a formidable opponent in the general election — assuming he wins the nomination.  If Thompson gets in, though, other Republicans such as Attorney General J. B. Van Hollen may have second thoughts about their own bids.  Either way, the nearly sure hold with Kohl may well turn into a lost seat.