By Andy Sullivan and Susan Cornwell
WASHINGTON (Reuters) - Republican Senator Susan Collins, an independent-minded moderate, won a surprise re-election victory in Maine on Wednesday, strengthening her party's chances of retaining control of the U.S. Senate.
Collins, 67, turned back one of the strongest challenges in her career as she defeated Democrat Susan Gideon, 48, the speaker of the Maine State House of Representatives.
"I feel that this is an affirmation of the work that I'm doing in Washington to fight hard every day for the people of Maine," Collins told reporters.
Gideon said she called Collins to concede.
"I congratulated her on winning this election, and I told her I would always be available to help serve the people of Maine," she said in a video broadcast on Facebook (NASDAQ:FB).
The result is a setback for Democrats, who hope to pick up at least three seats to win control of the 100-seat Senate. Collins had been viewed as one of the more vulnerable Republicans.
Gideon had led most opinion polls since July, as she argued that Collins had sacrificed her independence in support of Republican President Donald Trump, a divisive figure in the New England state.
But with 75% of expected votes counted, Collins led Gideon 49.8% to 43.4%, according to Edison Research.
Collins voted with Trump two-thirds of the time, according to the FiveThirtyEight website, making her the Senate Republican who was least aligned with the president.
She often served as a crucial swing vote in high-profile debates. She broke with her party to defeat an attempted repeal of the Affordable Care Act, popularly known as Obamacare. But she voted for Trump's sweeping tax cuts and voted against removing him from office after he was impeached by the Democratic-controlled House of Representatives.
She voted to confirm two of Trump's Supreme Court nominees, Neil Gorsuch and Brett Kavanaugh, but voted last month against confirming another, Amy Coney Barrett.
That vote put her in Trump's crosshairs, as the president complained on Twitter that she was "not worth the work."
Maine has a history of electing moderate Republicans. But politicians like Collins have become less common in Congress in an era of sharp political polarization.
Collins has held the seat since 1997. She last won re-election in 2014 with more than 68% of the vote.