President Barack Obama held a respectable lead in Wisconsin for months, before Mitt Romney chose Rep. Paul Ryan as his running mate and winning the state became a real possibility for Republicans.
The "Ryan effect," along with Wisconsin's dramatic shift toward the Republican Party in the 2010 midterm election, has made it possible for Obama to lose a state he won by a near-landslide 14 points in 2008.
A week before the presidential election, the race is still tight, with several polls giving Obama only a slight edge where he once had a sizable lead. ABC News rates Wisconsin as a "toss up."
With all this at stake for both parties, it's no surprise that Wisconsin is a hot spot for political travel in the final weeks of the election.
Before Hurricane Sandy preempted this week's campaigning, the state was expecting visits from both Obama and Romney this week alone. Vice President Biden stumped at the University of Wisconsin Friday and will return to the state this week. Bill Clinton will also stand in for Obama this week.
Ryan returned to his home state on Tuesday for a storm relief event and he was joined by Thompson. Ann Romney was also in the state for campaign events on Tuesday. He will attend several more events in the state today.
Down ballot, Democrats' and Republicans' hopes of keeping or taking the U.S. Senate could also rest on the race between Democratic Rep. Tammy Baldwin and former Republican Gov. Tommy Thompson.
If Thompson wins, Wisconsin would have two Republican senators serving in Congress for the first time since the 1950s, when Sen. Joe McCarthy (of the McCarthy hearings infamy) was the state's junior senator. If Baldwin wins, she would help preserve a Democratic Senate majority and would become the only openly gay senator in Congress.
In ad after ad, Baldwin and Thompson have gone heavily negative. Baldwin accused Thompson of having investments linked to Iran in a recent ad, and Thompson fired back, calling Baldwin "anti-Jewish" and "anti-Israel."
"This is an epic showdown between two people who have deep roots in the state," University of Wisconsin-Madison professor Barry Burden said. "It's been heavily negative, particularly in the advertising, but it's also carried on into the debates.
"They've been harsh towards one another. I guess they feel like they need to be."
Thompson's central argument against Baldwin, that she is too liberal for the state, perhaps encapsulates the state of politics in the Packer State of late.
Professor Burden says Wisconsin voters have a long history of electing progressive candidates such as Baldwin, but they have also been capable of endorsing more conservative candidates such as Walker and Johnson in 2010, and potentially Thompson in November.
The electorate is "very practical, looking for solutions to problems," Burden said.
With the presidential campaigning in Wisconsin intensifying in the final weeks, and the level of acrimony in the Senate race between Baldwin and Thompson increasing, battle-weary Wisconsin voters have a final set of difficult choices to make this November.
"It has been a very long year, politically speaking," professor Burden said. "The November election will be the sixth election in 2012 in the state. Voters have hit a point of saturation where advertising is not having a tremendous effect. People's opinions are pretty well formed."
In 2010, the political tectonic plates shifted in Wisconsin perhaps more than in any other part of the country. Voters ousted the state's Democratic governor and installed a Republican one, Scott Walker. Longtime progressive Democratic Sen. Russ Feingold was replaced by Tea Party-backed Republican Ron Johnson and Republicans also took control of the state Senate.
After Walker attempted to roll back collective bargaining for public employees once taking office in 2010, Democrats' hopes of making the state ground zero for the defense of collective bargaining union rights flopped with their failed bid to recall Walker in 2012.
Beyond Wisconsin's 10 electoral votes - a veritable bounty in a race that is expected to be won by razor-thin popular and electoral margins - the Romney campaign hopes to pluck Wisconsin out from under the nose of Democrats and deliver a win in Ryan's home state.
Two things will be crucial in the final days: unemployment in the state and early voting.
After reaching a high of 9.2 percent in 2010, Wisconsin's unemployment rate has decreased to 7.3 percent, dropping two-tenths of a percent in the past month alone
Just as Obama was elected in 2008 by voters who hoped he would bring much-needed economic change, his fate in 2012 could rest on their perceptions of the current economic conditions.
And Democrats are also hoping to mobilize younger, progressive voters to the polls this November. Wisconsin's "absentee voting" laws allow anyone to register at the election clerk's office prior to the election and cast an absentee ballot.
"The Democrats in particular are counting on last-minute registrations of young people and other people who are likely to register late," professor Burden said.