Sheehy led Tester 53%-45% when the race was called by the Associated Press at 6:26 a.m. EST on Wednesday.

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The bitter contest was the most competitive in the country as the de facto majority-maker seat, holding the most sway over which party would control the Senate.

In addition to helping propel Republicans back into the Senate majority in Washington, Sheehy’s win means that the GOP in Montana will achieve a feat only seen once before in the state’s history: A sweep of its Senate seats, governor’s mansion, and both legislative chambers at the same time. Republicans have not concurrently held them all since 1896.

Tester’s bid for a fourth term slowly slipped away in the campaign’s final months, as election forecasters and polling gave Sheehy the upper hand heading into the election.

The contest was the costliest in Montana’s history and the most expensive Senate race on a per-vote basis in U.S. history. Some $250 million was spent between Democrats and Republicans in a state with a population of just over 1.1 million.

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Sheehy, a former Navy SEAL and wealthy business owner, faced several controversies in the campaign’s closing months, including discrepancies over why he was discharged from service and how he obtained a past bullet wound, making racially charged remarks about Native Americans, and scrutiny over the aerial firefighting company he founded.  

Still, the Republican challenger eked out a victory that was buoyed by former President Donald Trump at the top of the ticket, who carried the state by double digits.