A few weeks ago, Wisconsin looked like a walkover for Democrats, in both the presidential and Senate races. Russ Feingold came out of retirement for a rematch against Ron Johnson, whose campaign-energy level had appeared to be flagging over the last year or so, and Donald Trump laid an egg in the state early. Democrats counted on flipping the state as one of their keys to a new Senate majority, and up to now have not appeared concerned with their progress.

Now, however, a super-PAC is making a $2 million, last-minute jump to boost Feingold, raising questions about what Democrats are seeing in the race. Alex Roarty reports on the infusion at Roll Call:

A Democratic Super PAC is making a surprise major investment in the Wisconsin Senate race in the election’s final days, a sign that a race many Democrats had long considered a sure victory has become unexpectedly tight.

Senate Majority PAC plans to spend $2 million on behalf of former Democratic Sen. Russ Feingold, who faces GOP Sen. Ron Johnson. The ads will run on broadcast and cable TV.

Roarty’s Democratic sources insist this is just a side benefit of a lucrative fundraising cycle. They’re also dropping more money into Florida, where Patrick Murphy trails significantly behind Marco Rubio, prompted in part by public complaints from Florida Democrats of their earlier decision to bail out of the Sunshine State. But Senate Democrats had canceled ads in Wisconsin, too, as Chris Cillizza reminds us, for the opposite reason:

Republican-held Wisconsin and Illinois will finish the election cycle on our rankings where they started: Most likely to flip parties. The Republican incumbents are running in states that lean blue in a presidential year. In Wisconsin, Clinton is up by almost 7 points, and it’s hard to see how Sen. Ron Johnson (R) can beat a well-known opponent who’s led him in almost every single public poll but one. Earlier this month, Senate Democrats’ campaign arm canceled ads in this state, suggesting they think former senator Russ Feingold (D) won’t have trouble closing, which is probably a safe bet.

If they’re back, what does that say about Wisconsin now? RealClearPolitics puts Feingold up by 6.3 points in their average for the race, but that includes a Feingold +12 outlier and a Monmouth poll (Feingold +8) with a sample of only 403 respondents and a margin of error at ±4.9 points. The gold standard of Wisconsin polling, Marquette Law, had Feingold up only two points in early October. That poll’s big takeaway was a voter shift to Hillary Clinton after the release of the Access Hollywood tape — and that showed Johnson narrowing the gap from five points to 46/44.

Can Johnson pull off a big upset? And how big of an upset would it be? Right now, FiveThirtyEight puts his chances of winning at, er … 5.9%. That’s far worse than the odds of the GOP holding the Senate (29.8%), or even a win by Trump in 11 days (17.9%). If Senate Democrats believed the odds were that low, though, they’d have sent that money to Nevada to protect Harry Reid’s seat from a Republican takeover by Joe Heck, who has a 46% chance of winning in FiveThirtyEight’s model. When Wisconsin voters start seeing the double-digit price hikes on the ObamaCare exchange, Johnson could find a way to close the sale in the final week. And that may be the real reason that Senate Majority PAC will drop big cash in that same period.