Former Sen. Russ Feingold (D-Wis.) is keeping his options open when it comes to the open Senate seat in Wisconsin, but state Democrats are increasingly skeptical that he’ll jump back into the fray after his loss in November. Linda Davidson/THE WASHINGTON POST (Linda Davidson/THE WASHINGTON POST)

Following Sen. Herb Kohl’s (D-Wis.) announcement two weeks ago that he wouldn’t seek reelection, observers have focused squarely on the two big names being mentioned: former governor Tommy Thompson (R) and former senator Russ Feingold (D).

Such a matchup, as we’ve noted before, is rare when it comes to Senate races. This year’s likely matchup in Virginia between a former governor (Democrat Tim Kaine) and a former senator (Republican George Allen), is a rare exception.

And it looks like Wisconsin’s open seat race will be the rule not the exception.

Sources say Thompson’s advisers are telling people that he’s 90 percent in, but Democrats in the know note that Feingold is showing very little interest in a return to politics so shortly after his loss to now-Sen. Ron Johnson (R) in the 2010 election.

Feingold’s outreach to his political advisers has been limited in the days since Kohl’s announcement, and already the conversation among the state’s Democrats has turned to alternatives.

“My read is that he’s not going to run,” said one high-level Democrat close to the race, noting that Feingold has shunned public appearances in recent weeks, including the state party convention scheduled for next weekend.

Feingold has the luxury of time, of course, due to his high name identification among Democratic primary voters and proven ability to raise money. Most party insiders acknowledge that he has the right of first refusal in the primary and, having just wrapped up a Senate campaign a few months ago, would have little trouble ramping things up again in a brief period of time.

A source close to Feingold emphasized that, while it’s clear he enjoys his time outside the Senate, which has included teaching at Marquette University law school and writing a book about foreign policy, he also hasn’t ruled anything out.

“He’s making it clear to people that he’s keeping his options open, that he doesn’t feel like he’s rushed into a decision,” the source said.

At the same time, with Thompson dipping his toe in the water, it puts some pressure on Democrats to try to bring clarity to their candidate slate in the near future.

The Republican was popular during his four terms in the governor’s mansion in the 1980s and 90s, and if he can survive a GOP primary, which is an open question given the tenor of Republican primaries these days and Thompson’s somewhat unhelpful record, would be formidable in a general election.

If indeed Feingold doesn’t run, the options include Reps. Tammy Baldwin and Ron Kind, who have both expressed interest in the race. Former Rep. Steve Kagen (D) is also telling people he will run but isn’t a favorite of the Democratic establishment. An outside possibility is Bucyrus CEO Tim Sullivan, who could self-fund millions once his company completes its pending sale to Caterpillar.

(There is, however, some question about which party banner Sullivan would run under. Democrats have been reaching out to him, but Republicans think he’s one of their own. Bucyrus spokeswoman Amy Malingowski told The Fix: “He’s not going to provide an answer to that at this time.”)

Assuming that the primary comes down to Baldwin and Kind, it presents Democrats with a tough dilemma.

Baldwin ranks as the most liberal member of Congress in the most recent National Journal vote rankings, and she was also the first openly gay member of Congress. She would be able to raise gobs of money from women’s and gay and lesbian groups nationally if she were to jump in.

In other words, she would be very formidable in the primary but would have to convince Democrats that she’s viable in the general election. (There still has yet to be an openly gay member of the Senate; Baldwin represents a very liberal enclave based in Madison.)

One source says Baldwin is polling both the primary and general election, and that she’s not going to jump into the race unless she sees a path to victory in both.

Kind, on the other hand, has the kind of centrist profile that like would do well in the general election. He’s won repeatedly in a swing district and has been eyed for statewide office for a while now.

But his base in the southwestern part of the state isn’t ideal for a primary. He would likely struggle to gain votes in Baldwin’s base of Madison and is completely unknown to Democrats in the eastern part of the state. Given Baldwin’s liberal bona fides and fundraising potential, it’s hard to see Kind beating those odds.

Of course, Thompson isn’t as likely to clear his primary under any circumstances and Democrats can still hold out hope of a clear primary if Feingold decides to run.

In other words, both sides have plenty to resolve in the weeks and months ahead. What’s clear, though, is that this swing state should be among the most competitive Senate races in the country come 2012.