North Dakota is home to one of the most important Senate races of 2018, and less than three weeks before Election Day, it’s embroiled in a fierce battle over who will be able to participate.

On Oct. 9, the Supreme Court allowed a new state voter identification requirement to take effect, meaning North Dakotans will be voting under different rules than in the primaries just a few months ago. The change disproportionately affects Native Americans, and tribal leaders and advocacy groups have spent the past week and a half scrambling. In a recent letter to the North Dakota secretary of state, one group called the state’s current process unworkable and proposed a solution, but the secretary of state would not endorse it.

It is an extraordinary situation: the electoral process thrown into chaos at the last minute in a state that will help decide which party controls the Senate. Here’s a look at where things stand.

Why is everyone talking about this?

The stakes couldn’t be much higher. Senator Heidi Heitkamp, a Democrat, is in an extremely tough re-election race in a state that President Trump won by 36 percentage points. If she loses, Democrats’ chances of taking the Senate, already pretty small, become minuscule. She’s behind in the polls, and if turnout is low among Native Americans — who helped elect her in 2012 — it will be all but impossible for her to come back.