The Wisconsin Senate race between Congresswoman Tammy Baldwin and former governor Tommy Thompson could well determine which party controls the U.S. Senate.
Polls show Tammy and Tommy in a virtual tie. Just five days ago, the final Marquette Law School poll -- a poll widely respected on all sides -- had Tammy up by 4 points -- one point better than the margin of error.
This had to be a major reason that President Obama chose to hold a big rally in Madison, Wisconsin, on what he described in his speech as "the last day I will ever campaign."
Obama is up by 8 points in that same Marquette poll.
But connecting with his base, creating some great pictures of tens of thousands of enthusiastic progressives -- and putting Tammy over the top -- led him to make his closing argument in Madison.
The first shout-out to another politician in Obama's speech was for Tammy.
He plugged her several times, describing her campaign and his as championing ordinary Americans.
If Tammy wins, it will be the biggest progressive victory of 2012.
Derided by her opponent in ads as "the most liberal member of Congress," Tammy was counted out early on. She started the race with almost no statewide name recognition -- and then jumped ahead of the best-known figure in state politics by 6 to 9 points right out of the blocks, according to several September polls.
In her Congressional career since 1998, Tammy Baldwin has stood for core values that her Democratic colleagues sometimes forgot. She opposed the repeal of the Glass-Steagall banking regulation during the Clinton years. She consistently voted against trade agreements that hurt American manufacturing and shipped jobs overseas.
But this year, in the last three months of the 2012 Presidential campaign, the national party's message has resonated more and more with Tammy's.
So in-tune is she with the Obama campaign, she got a Thursday night speaking slot at the national convention, and opened for Obama in rally after rally this fall in Milwaukee and Madison.
In her stump speech, she hits on the same progressive themes as Obama: the auto rescue, bank regulation, expanding health care (Baldwin wrote the provision of the Affordable Care Act that lets adult children stay on their parents' insurance).
Most of all, she describes her philosophy and the philosophy of her party as one of "fairness." Let the rich pay their fair share of taxes. Let gay people enjoy the same marriage rights as every other citizen. (Baldwin would be the first openly gay Senator and the first woman Senator elected from Wisconsin.)
Obama picks right up where she leaves off.
Beginning by talking about how the nation pulls together in times of crisis like Hurricane Sandy, the President said: "We're in this together."
That sentiment, he told the crowd, "has guided our great nation on this improbable journey."
Obama emphasized the Democrats' message, captured by the song that plays each time he walks off the stage: "We Take Care of Our Own." (At the Madison rally on November 5, he got back-up from Bruce Springsteen, who played, sang, told jokes, and gave Obama his hearty endorsement.)
Obama acknowledged progressives' frustration -- a particularly resonant message in Madison, where the crowd gathered around the Capitol looked so much like the protests Obama skipped here last year.
"Wisconsin, you know me by now. You may be frustrated at the pace of change," he said. "You may not always like my decisions.... But after all we've been through together, we can't give up now."
"We've made progress these last four years," Obama argued. "The reason we're gathered here, in addition to listening to Bruce, is we've got more work to do," Obama said.
No doubt about it: Wisconsin progressivism is a key ingredient in this national election.
The Obama campaign has even adopted Wisconsin's state motto "Forward!" as its campaign slogan.
So Obama came to Wisconsin to connect with progressives -- and to make the case that the choice is clear between the two sides in this election. To clarify it further, he sounded a lot like Baldwin:
"Giving more power back to the biggest banks -- that's not change," he told the crowd.
And: "We can't just cut our way to prosperity."
"I'm not going to kick some poor kids off of Head Start just to give me another tax cut."
Of his Republican opponents, he said: "Their bet is on cynicism. But, Wisconsin, my bet is on you."
Obama will most likely win Wisconsin. But the biggest bet of all will be on Tammy Tuesday night.
If you liked this article by Ruth Conniff, the political editor of The Progressive, check out her story "Romney Voter Fraud in Wisconsin." 
 Follow Ruth Conniff @rconniff  on Twitter.
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