New polls [3] show Rep. Tammy Baldwin, the Democratic candidate for Wisconsin's vacant U.S. Senate seat, with a four-point lead over her Republican challenger, former governor Tommy Thompson, in a race which may determine control of the Senate and had previously been considered a lock for Republicans. If Baldwin is elected she would likely follow in the footsteps of Wisconsin's Russ Feingold and be one of the more independent and progressive members of the U.S. Senate.

Outside groups like Karl Rove's Crossroads GPS and David Koch's Americans for Prosperity are spending millions on ads tagging Baldwin as "too liberal" for Wisconsin, and a variety of Democratic groups have criticized Thompson for his work at a lobbying firm with ties to outsourcing, helping make the state's close Senate race the second-most expensive [4] for outside money in the country [5] and the most expensive [6] in state history. The intensity of the race has also made it exceptionally negative [7], underscoring how close the race has become and its national importance.

Baldwin's Success Defies Odds

Baldwin's success in the race has surprised many, as some observers had speculated Wisconsin was on its way to becoming a red state. In just the past two years, it elected Scott Walker [8] as governor not once, but twice, and replaced liberal U.S. Senator Russ Feingold with Tea Party favorite Ron Johnson.

But Baldwin has gained support across the state by touting her strong record [9] on trade policies that help workers rather than global corporations, appealing to Wisconsinites who work in the manufacturing and paper industries. Her first TV ad [10], for example, highlighted her support for "Buy American" provisions that would require the government to buy U.S.-made paper, and her efforts to crack down on Chinese government-subsidized imports. She has also criticized [11] her Republican challenger Tommy Thompson for his work at a company that taught businesses how to outsource jobs, a message also advanced by independent groups spending to support her.

In recent weeks, the Koch-linked American Future Fund [12] has attacked this record head-on with deceptive ads [13] saying Baldwin supported EPA policies that would allegedly shut down eleven paper factories in the Fox River Valley, and Crossroads GPS [14] has blanketed the state with mailers saying Baldwin's support for Obama's jobs bill means she supports creating jobs in China.

Baldwin has also proven to be an effective fundraiser. She has out-raised Thompson, $11.2 million to $5.7 million, but outside groups have helped level [15] the playing field.

Thompson "He's Not For You Anymore"

Baldwin's success is even more surprising given that her challenger has long remained popular statewide and was widely expected to win. As Wisconsin's governor from 1987 to 2001, he governed as a moderate conservative and was reelected with wide margins [16]. During the hard-fought 2012 GOP U.S. Senate primary, though, his moderate roots made him a target for out-of-state groups seeking to anoint a more conservative candidate. He was attacked in ads [17] portraying him as a liberal from Super PACs like Club for Growth [18] and dark money groups like Americans for Job Security [19], which pushed [17] Thompson into taking far-right positions to survive the primary.

Since the primary, Thompson has been further attacked by groups supporting Baldwin that push the message he has changed since his time as Wisconsin's governor. In addition to criticizing his positions on taxes and outsourcing, the ads highlight Thompson's work at a Washington DC-based lobbying firm that represented the health care industry, after he was Health & Human Services Secretary under President George W. Bush.

Majority PAC has spent $2.9 million [20] on the Wisconsin race and has run ads [21] stating Thompson "made millions on K Street, working for a DC lobbying firm...how could Thompson ever represent us?" Women Vote!, the Super PAC for Emily's List, has spent $2.3 million [22] and has run ads [23] pushing a similar message, noting that Thompson "worked for a big DC lobbying firm" where he was "paid over $10 million as a DC insider, peddling his influence for the special interests." The Super PAC for public employee union AFSCME, AFSCME People, has spent [15] $1.7 million on the race and is running ads [24] pointing out Thompson's work for a "big DC lobbying firm, selling his influence to health care companies. Making millions helping insiders at our expense."

The Baldwin campaign has been pushing a similar message that "Tommy" has changed since he was Wisconsin's governor, running a series [25] of ads [26] that end with the message "Tommy Thompson. He's not for you anymore."

The Democratic Senatorial Campaign Committee has also spent [15] $7.1 million in Wisconsin, most recently running ads using footage of Thompson at a Tea Party meeting saying, "Who better than me ... to do away with Medicaid and Medicare."

9/11 a Major Campaign Issue -- in Wisconsin, 2012?

Despite huge differences between the candidates on healthcare, entitlement programs, and tax and trade policy, in recent weeks the issue that has dominated the race has been the September 11, 2001 terrorist attacks.

The Thompson campaign rolled out a scathing ad on October 23, "Dangerous Path," [27] that over images of charred buildings and fliers of missing persons from 9/11 accused Baldwin of disrespecting victims of the attack by voting against a symbolic resolution in 2006. Baldwin replied [28] that she voted for nine similar resolutions honoring 9/11 victims, but opposed this one in protest of language praising the USA PATRIOT Act, which incidentally puts her in good company -- Wisconsin's former U.S. Senator Russ Feingold was the lone vote in the Senate against the PATRIOT Act.

Baldwin responded [29] with her own ad two days later, referencing her efforts to honor 9/11 victims and attacking Thompson for profiting off of the 2001 tragedy when he was paid $3 million from a company that won a contract to handle health care for first responders, but was slow to provide care.

On October 28, Thompson responded with another TV spot critiquing Baldwin's ad and making the preposterous claim she "fought to block funding that provides body armor for our troops just to make a political point." Baldwin had supported a bill that would have allowed conscientious objectors to direct their income taxes towards non-military needs, rather than war, but "the notion that, if this bill would pass, it means that Tammy Baldwin would be denying body armor to troops, is ludicrous," said [30] Kenneth Mayer, professor of political science at the University of Wisconsin-Madison.

The Thompson campaign sourced the inaccurate claim to Media Trackers, a right-wing "media watchdog" group funded by American Majority [31] that recently made headlines for hyping a brutal lie [32] about the partner of the Democratic candidate seeking to replace Baldwin in the U.S. House, suggesting he threatened and assaulted a Republican volunteer.

The candidates have also traded barbs over Iran. Thompson criticized Baldwin for accepting campaign contributions from the Council for a Livable World, an anti-nuclear group that opposed sanctions against Iran (which the Thompson campaign portrayed as a "pro-Iran" group), and Baldwin knocked Thompson for owning shares in a company that traded with Iran.

In Wisconsin -- a state that has been slow to recover from the economic crisis, whose economy depends on agriculture and manufacturing, and whose residents are struggling with healthcare costs and coverage -- the 9/11 tragedy may not be a top issue in voter's minds. But the fact that the campaigns are digging this deep to find new angles is indicative [33] of just how strong Baldwin's appeal is and how close this race has become.

Thompson Support from Koch Brothers, ALEC Member ACC

In addition to attacking Baldwin with far-fetched 9/11 allegations, Thompson has run a series of ads calling his challenger "too extreme" for Wisconsin, citing her past support for single-payer health care and for supporting a budget plan from the Congressional Progressive Caucus.

The "too extreme" message has also been pushed by outside groups spending millions on ads. Karl Rove is dropping $2.3 million on just one week of ads [34] to try and reverse Baldwin's fortunes, for a total of nearly $6 million [15] from his dark money group Crossroads GPS and his related Super PAC American Crossroads. Baldwin has also been attacked by at least $2 million [15] in ads from David Koch's Americans for Prosperity, [35] including one from earlier this year that framed the results of Governor Scott Walker's recall election as a statewide consensus on wasteful spending and describing Baldwin as "part of the problem." The Emergency Committee for Israel [36] has also spent $500,000 on inflammatory anti-Baldwin ads [37].

Thompson has received significant outside support from chemistry industry trade group the American Chemistry Council, [38] which has spent nearly $649,000 [39] on positive pro-Thompson ads. He is the top beneficiary of spending by the chemistry group, which is seeking to block efforts to update the 36-year-old Toxic Substances Control Act on the federal level, and is a member of the controversial American Legislative Exchange Council [40] (ALEC).

Thompson has long ties to ALEC [41] and has received awards from the right-wing organization. His ALEC ties have not become a central issue in the campaign, but some reporters have questioned him about it, including the Milwaukee Journal Sentinel's top reporter Dan Bice [42]. The Progressive Change Campaign Committee has used the connection [43] to recruit volunteers for Baldwin.

Baldwin Would be First Openly Gay U.S. Senator

If elected, Baldwin would be the first openly gay U.S. Senator in history, and at least some of the money spent backing her (or attacking Thompson) is traceable to gay rights supporters. The top donor to Women Vote! [44] is the Gay & Lesbian Victory Fund (GLVF), which has given $325,000; GLVF has also contributed $10,000 [45] directly to Baldwin's campaign. Chicago media mogul Fred Eychaner is a top Democratic donor and major funder of LGBT rights organizations, and has donated $800,000 [46] to Majority PAC and $50,000 [47] to GLVF. He has previously described [48] Baldwin as one of his personal heroes.

Thompson has not yet made an issue of Baldwin's sexual orientation, but his silence on the issue has not stopped his supporters. In September, Thompson's campaign manager sent an email and tweeted [49] a video of Baldwin dancing at a gay pride parade with a message questioning her "heartland values." State Senator Glenn Grothman issued a news release criticizing Baldwin's "radical agenda" (the same claim made by the Thompson campaign), but specifically and erroneously [50] claimed that Baldwin introduced a bill that would force doctors to ask patients about their sexual orientation. In recent weeks, CitizenLink, a group associated with the Religious Right organization Focus on the Family, has begun sending mailers and running internet ads [51] attacking Baldwin for supporting gay marriage rights, and internet ads have appeared from the group Public Advocate criticizing Baldwin for advancing the "Homosexual Agenda." Others, such as the Washington Times [52], have urged Thompson to focus on Baldwin's sexual orientation -- and it remains to be seen whether he will do so in these final days.

Polls Bounce Back and Forth, Following National Trends

Polling [53] showed Thompson leading Baldwin significantly through August, according to some polls by double-digits. But after the August 5 primary the Thompson campaign took a break, during which time Baldwin and her supporters ran ads increasing her name recognition with Wisconsinites and re-framing Thompson as a DC insider.

In addition to the ad spending, the Thompson-Baldwin poll numbers have been strongly affected by national trends. Baldwin took the lead in September, after the Democratic National Convention, when Obama also began polling well, and retained it throughout that month as Democrats led nationally after Romney's controversial 47% video. The Wisconsin Senate race, like the presidential race, has narrowed in recent weeks [54] after the Republican surge following the first presidential debate.

Though polls currently show [3] Baldwin with the lead, among likely voters the race is a virtual tie, and the outcome may depend on the presidential race. "The two votes are very, very highly correlated, much more so than they were earlier in the year," said [33] Charles Franklin, director of the Marquette University Law School poll.

Still, Wisconsin's truly independent voters can be unpredictable -- as many as 12 percent [55] of Wisconsin voters who supported Governor Scott Walker in last June's recall will also support President Obama's reelection.