When one talks Republican policy and politics, from the size and cost of government to the role of some notoriously out-sized GOP enemies such as public sector unions, including in education, there may not be a more critical battle space nationally-speaking, than Wisconsin this year.

Democrats have been gunning for incumbent Gov. Scott Walker since he and the Republican-controlled state legislature passed Act 10 — a measure curbing the collective bargaining powers of some public workers — forcing them to contribute more for their health care and pensions, and ending the automatic collection of union dues.

It’s hard to remember the incredible intensity that surrounded passage of Act 10 three years ago. Democratic lawmakers fled the state rather than allow a vote on it. Protesters took over the state capitol. There was an ugly Supreme Court fight. But it became the law.

As the GOP struggles to capture the Senate, those races have been rising and falling on issues like immigration, the economy and even foreign policy. But as important as those may be, the issues at the heart of Wisconsin Gov Scott Walker’s re-election bid are perhaps even more critical to the success of any larger national GOP agenda. 

And Democrats know it, ” “We have a score to settle with Scott Walker. He took collective bargaining away from us. He stole our voices, in a state where we were born,” Lee Saunders, president of the American Federation of State, County and Municipal Employees told the Washington Post.

In the years since, Act 10 has been very good for the state budget. The measure has saved the state somewhere between $2 billion and $3 billion, mostly in pension costs.

On the other hand, Act 10 has been very bad for public-sector unions. “We’ve lost 70 percent of our membership in the state,” Lee Saunders, president of the American Federation of State, County and Municipal Employees, told the Washington Post recently. Teachers’ unions have also been hit hard.

Walker’s law is the most devastating blow ever struck to union domination of public services. It is probably not an exaggeration to say that revenge-seeking organized labor will pursue Walker to the grave, and perhaps beyond. This year, AFSCME, the AFL-CIO and others will spend tens of millions, perhaps more than $100 million, in an effort to unseat him in favor of Democrat Mary Burke.

Consequently, political emotions in Wisconsin are running at a fever pitch, making it perhaps the only race this year that comes anywhere close to the intensity of a national campaign. Given that Scott Walker enacted the very type of reforms near and dear to many a right-leaning heart and he could end this year having survived perhaps the largest and nastiest combined assault from Democrats and the Left since 2012, it’s difficult to imagine how his survival wouldn’t position him as a key GOP figure when attention turns to 2016 almost as quickly as the mid-term votes have been counted.

The race is important to the national GOP for two reasons. One is that a Walker victory would validate and solidify Act 10, while a loss would undermine it. The second reason is that Walker may well be a contender for the 2016 Republican presidential nomination — but only if he wins re-election first.

Walker is already admired in GOP circles for his stand against the unions. A victory could further strengthen his appeal in early-voting Iowa. “If Scott Walker, for a third time, puts up a GOP victory in a blue state, it will be a selling point that would be difficult for other candidates to match,” says David Kochel, a veteran Iowa Republican strategist.

While not exactly a secret, the race hasn’t gotten the attention of some of the big Senate showdowns. “The race may be flying under the radar because folks assumed Walker would be re-elected, given his success in the recall,” says Charlie Sykes, a local radio host. But Sykes reminds that President Obama won Wisconsin twice, and the governor still faces “the persistence of Walker Derangement Syndrome and the commitment of national unions to take him out.”

Polls show the race essentially tied. A new Marquette University survey shows Walker ahead by three percentage points among likely voters, which is within the poll’s margin of error. Republicans are right to be nervous.

Of course, despite all he has faced, Walker has prevailed before. The GOP needs him to do it again.