Perhaps the most surprising election in America right now is the tight battle for a U.S. Senate seat in Nebraska. Dan Osborn, a union leader running as an independent populist, is functionally tied with Sen. Deb Fischer, the incumbent Republican. The latest New York Times/Siena poll has Fischer leading by two points, well within the margin of error. Other polls show Osborn in front, and even in the Siena poll, he’s ahead among registered voters.

The situation has left many wondering why Fischer, who has mostly lain low during her two terms in the Senate, would be in any trouble in a red state. But a sleeper issue sheds light on what Osborn’s challenge is really all about.

One of Osborn’s closing ads features a farmer and longtime Republican explaining why he turned against Fischer. “Senator Deb Fischer is a fake rancher … She got ten times richer in office, we pay her millions, and she can’t even pass a farm bill,” the farmer says, going on to make a pitch for Osborn over scenes of the candidate standing in a crop field and fixing a John Deere tractor.

Agriculture is clearly important in Nebraska, and the “fake rancher” issue—Fischer’s family ranch has been dissolved multiple times due to unpaid corporate taxes—amid indifference over a languishing farm bill could be resonant. But there’s a separate, more obscure history … that is, obscure unless you’re a rancher in Nebraska, and probably know the details well.