Some may wonder how a Senate race in Montana could be so close. After all, Mr. Trump won the state by 20 points in 2016. But Democrats successfully recruited Mr. Bullock, the state’s governor since 2013, who remains highly popular with voters even after his failed 2020 presidential run. His favorability rating is 53 percent (41 percent unfavorable), while just 48 percent had a favorable view of Mr. Daines, the incumbent Republican senator, and 44 percent held an unfavorable view.

Mr. Daines is counting on the state’s rightward lean to help overcome Mr. Bullock’s personal popularity. By a margin of 50 percent to 42 percent, Montanans in our survey say they prefer that Republicans control the U.S. Senate, and they back President Trump over Joe Biden by a similar margin of 49 percent to 42 percent.

The survey was conducted before the death of Ruth Bader Ginsburg on Friday, and Mr. Daines can hope that the state’s Republican lean will prove even more important during an intense battle for the direction of the court.