American voters on the Democratic Party’s mailing list may have been startled to receive an email last weekend with the subject line, “I have nowhere else to turn.” The email came not from a long-lost Nigerian prince looking for a small donation, but from the re-election campaign for North Dakota Senator Heidi Heitkamp.

Mrs. Heitkamp’s campaign hopes that out-of-state donations can help her close the gap to her Republican challenger and current North Dakota Congressman, Kevin Cramer. A recent poll by Fox News gave Mr. Cramer a twelve-point lead over the incumbent. Mr. Cramer has expanded his lead as the election approaches; an earlier Fox News poll from September showed just a four-point advantage to the G.O.P. candidate.

Senator Heitkamp’s position in North Dakota has long been tenuous. She won her first election to the Senate in 2012 by just 3,000 votes, out of more than 300,000 cast. The rise of Donald Trump in 2016 and the subsequent leftward shift of the Democratic Party has transformed North Dakota into reliable Republican territory. In the most recent presidential election, Mr. Trump won the state by 36 points.

On unstable political territory, Senator Heitkamp has excelled at finding the middle ground. She has built her campaign on the promise of bipartisanship. Her campaign’s website emphasizes family values and infrastructure, more common lynch-pins of Republican campaign platforms. According to political analysis website FiveThirtyEight, an affiliate of ABC News, Mrs. Heitkamp has voted with Mr. Trump 54% of the time, the second-highest support rate among Democrats (only West Virginia Senator Joe Manchin is higher).

When Senator Heitkamp diverges from Republican policy, she does so carefully. She is hoping to make gains among North Dakota soybean farmers who have been hit hard by Mr. Trump’s trade war with China. Soybean is North Dakota’s leading crop, with over seven million harvested acres in 2017 producing over two million dollars, according to a report by the USDA. Two-thirds of that crop was sold in China, where the demand for soybean-fed cattle has been driven by the rise of the prosperous middle class. In response to Mr. Trump’s inflammatory tariffs, China placed a 25% import tariff on American soybeans, leading to a sudden drop in overseas demand for North Dakota soybeans.

“We are now on the brink of a crisis in farm country that is completely policy-driven,” Mrs. Heitkamp said at the Big Iron Ag and Trade Forum in September. “It’s not being driven by weather. It’s not being driven by bad farmers…Why is it that we’re struggling? We’re struggling because we’re given bad policies.”

Voters are not turning away from Mrs. Heitkamp over her agricultural policies. The change in the polls is most likely due to the Brett Kavanaugh confirmation. The President’s Supreme Court nominee faced a bitter partisan nomination process after multiple women came forward with allegations of sexual assault by Justice Kavanaugh. Senator Heitkamp voted against confirmation, saying that she had “an obligation to do the right thing.” While the decision to vote on her conscience is admirable, it was also politically risky. A September poll conducted by Strategic Research Associates and NBC North Dakota News showed sixty percent of North Dakotan voters approved of Mr. Kavanaugh, with just twenty-seven percent against his confirmation.

The Heitkamp campaign has come under recent criticism as well. An open letter written on behalf of the campaign attacked Mr. Cramer over his recent comments on sexual assault. The letter included over 120 names, purportedly of sexual assault victims. However, multiple women named have either stated that they are not victims of sexual assault, or did not give the Heitkamp campaign permission to use their names in such an advert. Senator Heitkamp has issued a personal apology.

Senator Heitkamp’s electoral struggles are bad news for the Democratic party at large. Victories in the midterm elections would allow the Democrats to block Mr. Trump’s legislative efforts and government appointments. FiveThirtyEight’s generic ballot has them eight points ahead of the Republicans as of 17 October, giving them a high probability of winning the House of Representatives.

The race to take control of the Senate is another matter. The Republicans hold a slim 51-49 majority in the senior house; however, the Republicans are only defending nine seats in November. The Democrats are defending twenty-six, including two independent senators that caucus with the Democrats. The Democrats have a reasonable chance to flip Republican seats in Arizona, Nevada, Tennessee, and even Texas, but to retake the Senate they must defend their current seats vigorously.

This makes Heitkamp’s seat in North Dakota crucial to the overarching Democratic strategy. With such a poor electoral map, the Democrats can ill afford to lose ground to the G.O.P. Far left activists may complain that a state with less than half a percent of the country’s population should not play such an outsized role in deciding the makeup of the US Senate, but unless Mrs. Heitkamp and her supporters can engineer a comeback North Dakota might be the Democrats’ Waterloo.