Everyone knows the most important political race in the country this fall is the race that determines control of the U.S. Senate, which is very much up in the air. According to The New York Times prediction model, the deciding race would be North Carolina if the election were held today. Winning there would likely give Democrats a 50-50 split (assuming that two independents continue to caucus with them) and allow Vice President Joe Biden to cast a deciding 101st vote.

But what’s the second most important election in the country? You might be tempted to say it’s another competitive race like Louisiana, Arkansas, or Colorado. But I’d argue that the second most important election isn’t a Senate race at all. In fact, it’s one whose winner won’t even hold office in Washington, at least not right away. It’s the campaign for governor of Wisconsin, which pits incumbent Scott Walker against Mary Burke, a little-known executive at the bike manufacturer Trek. And it could shape U.S. politics for years to come.

Walker achieved conservative icon status by gutting collective bargaining rights for public-sector unions and preventing the unions from automatically deducting dues from members’ paychecks. The law he signed triggered a backlash from Democrats across Wisconsin and ultimately led to an attempted recall in 2012, while also causing the state’s public unions to hemorrhage members.

Walker survived the recall vote by a healthy 53-46 margin, and since then most of us who only vaguely follow the headlines from his state have assumed he’ll coast to re-election. But Walker is emphatically not coasting. His favorability rating has been under water for months. Polls consistently show the race a tossup, and Burke actually held a one-point lead among likely voters in the latest Marquette University Law School poll, the most respected survey in the field. It turns out there’s a sizable group of Wisconsin voters who didn’t believe Walker’s record merited a recall but don’t exactly love the guy either.

All of which is to say this is a very winnable race for Burke, provided Democratic donors give her the cash to compete with Walker, and that the Democratic base turns out in adequate numbers. (Burke is polling so well she only needs a solid rather than an amazing turnout—eminently doable even in a nonpresidential year.)