A source close to former Rep. Steve Kagen (D) says the ex-Congressman is considering running for the suddenly open Wisconsin Senate seat in 2012.

Kagen served two terms in the 8th district before being knocked off by now-Rep. Reid Ribble (R) last fall.

The source pointed out a handful of qualifications that could make Kagen a serious contender for the seat long held by Sen. Herb Kohl, who announced Friday he would not seek re-election. His attributes, according to the source, include being a doctor, two election wins in what is largely considered a swing district, his folksy manner and his ability to self-fund.

If he runs, Kagen won’t be alone. Democrats are floating names such as Tom Barrett, the Milwaukee mayor who ran for governor last year and narrowly lost to now-Gov. Scott Walker. Seven-term Rep. Tammy Baldwin is likely to run. Eight-term Rep. Ron Kind is also a Democrat to watch, as is former Sen. Russ Feingold, also unseated by a Republican last fall.