Senator Heidi Heitkamp, a blue outlier in a state where Republicans dominate, took pains to present herself as a moderate who was willing to side with President Trump and work across the aisle. Her efforts failed, however, and she lost her re-election fight to Republican opponent, Representative Kevin Cramer. Read more

Mr. Cramer, an ally of Mr. Trump, criticized Ms. Heitkamp for voting against the confirmation of Justice Brett M. Kavanaugh to the Supreme Court. Ms. Heitkamp then doubled down on her stance.

A new law that required voters to present identification at the polls that lists a street address could have also hurt Ms. Heitkamp, who trailed in recent polls. Many Native Americans in North Dakota live on reservations and have identification that lists a post-office box and not a street address. Native Americans are an important voting bloc in North Dakota, and they generally support Democrats.