Democratic Senate candidate Sara Gideon has conceded her race to Republican incumbent Susan Collins in Maine.
"Just now I spoke with Senator Collins. I congratulated her on winning this election," Gideon said in a concession speech Wednesday afternoon.
She also tweeted “I’m proud of the campaign we ran, regardless of the result.”
Collins faces a tight race and had a unique set of circumstances due to Maine's ranked choice process, which requires a candidate to reach a 50% threshold to claim victory.
CNN has not projected the winner of the US Senate race in Maine.
The defeat would be a major blow to Democrats, who have already come up short over the past 24 hours in a number of races where they were competing in hopes of flipping the chamber. Democrats' chances of controlling the Senate are now rapidly diminishing.
How does ranked-choice voting work?
Maine’s ranked-choice voting system lets voters literally rank their choices in order of preference, marking candidates as their first, second and third choice picks (and so on).
The winner must have a majority (more than 50% of the votes) rather than a plurality (simply the most votes).
In Maine, ranked choice only takes effect when three or more candidates are on the ballot. Voting is counted by round, with lowest-ranked candidates eliminated in each round until only two candidates remain.
See Gideon's tweet:
Correction: An earlier version of this post said Collins won the Maine Senate race. Democratic Senate candidate Sara Gideon has conceded, but CNN has not yet projected the winner of the US Senate race in Maine.