Republican Sen. Steve Daines is projected to win Montana's Senate race, NBC News projected early Wednesday.
He is expected to defeat Democratic Gov. Steve Bullock. The projected win ensures Republicans will hold at least 47 Senate seats in the next Congress, boosting the party's hopes of holding its majority after the 2020 election.
States with still undecided Senate races include Arizona, North Carolina and Maine.
First-term Republican Daines faced an unexpectedly competitive challenge from two-term Democratic Gov. Bullock. The governor, who can't run for reelection, first made a bid in the 2020 Democratic presidential primary before dropping out and shifting to Montana's Senate seat.
Montana's competition became one of the most expensive Senate races of the election season. Bullock's campaign spent more than $38.6 million while Daine's campaign spent about $26.1 million.
Polling averages suggested a neck-and-neck race between Daines and Bullock. Daines won his 2014 Senate race with 58% of the vote. Bullock won his 2012 and 2016 gubernatorial races by 2 and 4 percentage points, respectively. In 2016, President Donald Trump won the state by 20 percentage points.
Montana hasn't voted for a Democratic presidential candidate since 1992, but ticket splitting is not a rare occurrence in the state.