PORTLAND, Maine (AP) — The most expensive political campaign in Maine history has drawn to a close but votes were still being tallied to determine whether Republican U.S. Sen. Susan Collins is reelected to a fifth term or is ousted in favor of Democratic House Speaker Sara Gideon.

Collins has touted herself as an experienced, bipartisan candidate who works to get things done for Maine, and is in line to chair the powerful Appropriations Committee if Republicans retain control of the U.S. Senate.

Gideon, for her part, sought to drive home her message that Collins no longer represents the interest of Mainers after votes for Supreme Court Justice Brett Kavanaugh and for President Donald Trump’s tax cuts.

It was too early to declare a winner as vote counting continued early into Wednesday. It was possible that additional tabulations could be necessary under Maine's ranked choice voting system.

Collins told supporters Tuesday evening in Bangor that she never backed down in the face of a flood of negative ads in the race.

“The other side thought they could come to Maine and just run negative ads, dump loads and loads, millions and millions of dollars of money, and just buy the Senate seat," she said after polls closed, acknowledging it was early in the evening. “Is that the Maine way? No, it certainly is not.”

Gideon, for her part, did not appear at an event at a Portland hotel but said she was grateful to all of her supporters.

"It’s clear this race will not be called tonight and we are prepared to see it through to the finish. Over the coming days, we will make sure that every Mainer has their voice heard in this election,” she said.

The Senate race was the most costly in Maine's history with Gideon raising nearly $70 million, more than double Collins' $27 million. But that didn't include so-called dark money. All told, more than $120 million was spent by both candidates and outside groups on television advertising.

Polls showed a tight contest, despite all of the money. Mainers on Tuesday got the final say on the race, which also includes two independents, educator Lisa Savage — who hoped to become the first Green senator by rejoining the party — and conservative businessman Max Linn.

More than 500,000 Mainers already voted before Election Day and some polling places were crowded on Tuesday, causing delayed tallies from clerks in some municipalities.

A tight race could trigger provisions under Maine’s ranked choice voting.

The voting system lets people rank all candidates on the ballot. If no one wins a majority of first-round votes, then there are additional tabulations in which last-place finishers are eliminated and their second-place choices reallocated to the remaining field to assure a majority winner.

Democrats began targeting the popular Collins after her vote for Kavanaugh, and opponents crowdsourced money to unseat her. The Democratic Senatorial Campaign Committee gave an early endorsement to Gideon, who easily won her primary.

Changing demographics and partisan politics have altered the political landscape.

In the past, Collins easily won reelection with help from independents and even some Democratic voters in a state known for its fierce independence. But Democrats surged past independents in voter registrations this summer, becoming the state’s largest voting bloc.

Republicans cast Gideon as a wealthy liberal and a risky choice. Collins contended Gideon would be a Democratic partisan, not an independent voice, and touted her ability to get things done, pointing to the Paycheck Protection Program — for which she was lead author — as helping businesses during the coronavirus pandemic.

Gideon, meanwhile, said Collins’ seniority didn’t seem to give her much standing in her own party caucus. She vowed to press for a Medicare option for health care and environmental improvements while stopping short of the “Medicare For All” and Green New Deal proposals backed by progressives.

Collins is a native of Maine, raised in Caribou, where she picked potatoes as a kid, and touted her familiarity with Maine’s unique issues.

"I’ve always put you first. You and you alone are my priority and I have been honored to serve you, each and every day. That's that’s why I’ve never missed a single roll call vote," she said, noting that she's cast 7,486 consecutive votes in the Senate.

Gideon, originally from Rhode Island, moved to Freeport, Maine, about 15 years ago. She was elected to the Legislature in 2012 after serving on the Freeport Town Council.

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