Despite most observers initially labeling Thompson – who was reelected three times with wide margins and is known to most Badger State voters simply as “Tommy” – a shoo-in, the contrast between a grumpy, bombastic older man incredulous at the challenge and a younger woman appealing earnestly for every vote seems to be working in Baldwin’s favor.

“She’s been so measured and workmanlike and that stands in enormous contrast to Tommy Thompson, who has frankly embarrassed himself,” says Russ Feingold, the liberal champion and longtime U.S. senator here who was unseated at the height of the Tea Party wave in 2010. “He seems angry. He acts entitled to this position just because he’s Tommy, and people are sort of insulted by that. It’s not a very attractive image. He’s been bellicose.  Maybe people were into that in 2010 with the Tea Party, but Tommy’s a couple years behind – as he often has been.”

While Tammy Baldwin can be accused of many things, being behind the times is certainly not one of them. And those who know her best are not the least bit surprised by her political rise.

“What’s often happened with Tammy is that there are understated expectations, partly on the basis of her gender and sexual orientation,” says John Quinlan, a political activist and liberal radio host in the state who introduced Baldwin to her partner of 15 years (with whom she recently separated) and counts her as a friend. “She’s shown throughout her career that she can break through those barriers.”

There have been many such barriers, some thrown up by her own party elite; leading Democratic officials have sometimes fretted Baldwin was pushing too hard too fast.

“In ’98 when she was in the primary for Congress as the first out person, there was a lot of nervousness in Washington among Democrats and the DCCC,” Rep. Frank told me. Two years prior, anxious that a veto might damage his cruise to reelection, President Bill Clinton had signed the Defense of Marriage Act, a regressive bill that makes it harder for states to advance the rights of gay couples. President Obama has called for DOMA’s repeal, though he has yet to expend much political capital on the issue.

Even so, Obama’s shift on marriage could be particularly useful in Baldwin’s case, as polls have shown Democrats and African-Americans in particular warming up to marriage equality since his announcement. Baldwin is counting on robust turnout from Democratic base voters, such as those in Milwaukee’s black neighborhoods, to push her over the top.

To be sure, Thompson has received his own boost from outside groups like Karl Rove’s Crossroads GPS, which to date has spent about $5 million on TV ads painting Baldwin as an extreme Madison liberal who can’t be trusted. This would probably have been enough to close the deal were it not for the Democrat’s ability to excite gay and feminist donors like no other politician in America. She has raised about $11 million – second only to national liberal superstar Elizabeth Warren – and outside spending in the Wisconsin Senate race is surpassed only by that in Virginia, a stunning revelation when one considers that TV ad time is way cheaper in Wisconsin than in the pricey Washington, D.C., media market.

“The way we’ve been able to define him is so crushing,” said Maslin, the pollster and ad-maker for Baldwin’s allies.

Baldwin’s cultivation of gay and lesbian activists and donors since arriving in Washington has been a huge help. Some 76 percent of her regular campaign contributions have come from out of state, a greater proportion than any other Senate candidate in America. But she is also energizing unions and other more traditional segments of the Democratic base that appreciate her unapologetic progressive populism.

More than anything else, though, the chance to achieve another “first” – Wisconsin was the first state to pass a gay rights bill decades ago – has clearly captured the imagination of liberal activists here.

“She has a tremendous ability to motivate young voters, and that’s partially because of the historic nature of her candidacy,” says Chad Griffin, president of the Human Rights Campaign, which, like the Victory Fund, has deployed field staffers to the state.

Charles Franklin, the University of Wisconsin political sage whose Marquette University Law School poll commands wide respect in the state (and nailed Scott Walker’s recall margin of victory), pegs Baldwin’s lead at 47 percent to 43 percent in his final pre-election survey. Though 10 percent of voters remain undecided, he’s bullish on Baldwin’s chances, and credits the massive spending by the candidate and her allies with upending the race by completely reversing Thompson’s standing with voters.

“It’s remarkable that a figure of his stature in the state has had his image change that much,” he says.

Pigeonholing Baldwin as just a “gay candidate” would be a mistake, as much of her work has been on economic issues, like the popular provision in the healthcare law that allows kids to stay on their parents’ health plans until age 26. But she doesn’t deny for a second the significance of what a win means for gay rights.

“If you’re not in the room, the conversation is about you,” she told me in an interview in the backseat of her campaign SUV after a get-out-the-vote rally in downtown Milwaukee on a brisk Saturday late in October. “If you’re in the room, the conversation is with you. And If I’m elected to the U.S. Senate, that conversation will be transformed by virtue of the fact that I’m at the table.”