JUNEAU, Alaska — Democrat Mary Peltola won the special election for Alaska’s only U.S. House seat on Wednesday, besting a field that included Governor Palin, who was seeking a political comeback in the state.

Ms. Peltola, who is Yup’ik and turned 49 on Wednesday, will become the first Alaska Native to serve in the House and the first woman to hold the seat. She will serve the remaining months of the term of the late Republican congressman, Don Young. He held the seat for 49 years before his death in March.

“I don’t think there will be another birthday like today,” Ms. Peltola said.

“Really I’m just so grateful to Alaskans and all the Alaskans who put their faith in me to fill out the remainder of Congressman Young’s term,” she said in an interview. “My desire is to follow in Congressman Young’s legacy of representing all Alaskans, and I’m just looking forward to getting to work.”

Ms. Peltola’s victory, in Alaska’s first statewide ranked choice voting election, is a boon for Democrats, particularly coming off better-than-expected performances in special elections around the country this year following the Supreme Court’s overturning of Roe v. Wade. 

She will be the first Democrat to hold the seat since Congressman Nick Begich, who was seeking reelection in 1972 when his plane disappeared. Begich was later declared dead and Young in 1973 was elected to the seat.

Peltola ran as a coalition builder while her two Republican opponents — Ms. Palin and Begich’s grandson, also named Nick Begich — at times went after each other. Ms. Palin also railed against the ranked voting system, which was instituted by Alaska voters.

All three — Ms. Peltola, Ms. Palin and Mr. Begich — are candidates in the November general election, seeking a two-year term that would start in January.

The results came 15 days after the August 16 election, in line with the deadline for state elections officials to receive absentee ballots mailed from outside America. 

Ranked choice tabulations took place Wednesday after no candidate won more than 50 percent of the first choice votes, with state elections officials livestreaming the event. Ms. Peltola was in the lead heading into the tabulations, followed by Ms. Palin and then Mr. Begich.

State elections officials plan to certify the election by Friday.

Alaska Democratic Party leaders cheered Peltola’s win.

“Alaskans have made clear they want a rational, steadfast, honest and caring voice speaking for them in Washington D.C., not opportunists and extremists associated with the Alaska Republican Party,” the state Democratic party chairman, Michael Wenstrup, said in a statement.

Wednesday’s results were a disappointment for Ms. Palin, who was looking to make a political comeback 14 years after she was vaulted onto the national stage when Senator McCain selected her to be his running mate in the 2008 presidential election. In her run for the House seat, she had widespread name recognition and won the endorsement of President Trump.

After Ms. Peltola’s victory was announced, Ms. Palin called the ranked voting system “crazy, convoluted, confusing.”

“Though we’re disappointed in this outcome, Alaskans know I’m the last one who’ll ever retreat,” Ms. Palin said in a statement.

Mr. Begich in a statement congratulated Ms. Peltola while looking forward to the November election.

During the campaign, critics questioned Ms. Palin’s commitment to Alaska, citing her decision to resign as governor in July 2009, partway through her term. Ms. Palin went on to become a conservative commentator on TV and appeared in reality television programs, among other pursuits.

Ms. Palin has insisted her commitment to Alaska never wavered and said ahead of the special election that she had “signed up for the long haul.”

Ms. Peltola, a former state lawmaker who most recently worked for a commission whose goal is to rebuild salmon resources on the Kuskokwim River, cast herself as a “regular” Alaskan. “I’m not a millionaire. I’m not an international celebrity,” she said.

Ms. Peltola has said she was hopeful that the new system would allow more moderate candidates to be elected.

During the campaign, she emphasized her support of abortion rights and said she wanted to elevate issues of ocean productivity and food security. Ms. Peltola said she got a boost after the June special primary when she won endorsements from Democrats and independents who had been in the race. She said she believed her positive messaging also resonated with voters.

“It’s been very attractive to a lot of people to have a message of working together and positivity and holding each other up and unity and as Americans none of us are each other’s enemy,” she said. “That is just a message that people really need to hear right now.”

Alaska voters in 2020 approved an elections process that replaced party primaries with open primaries. Under the new system, ranked voting is used in general elections.

Under ranked voting, ballots are counted in rounds. A candidate can win outright with more than 50 percent of the vote in the first round. If no one hits that threshold, the candidate with the fewest votes is eliminated. 

Voters who chose that candidate as their top pick have their votes count for their next choice. Rounds continue until two candidates remain, and whoever has the most votes wins.

In Alaska, voters last backed a Democrat for president in 1964. The number of registered voters who are unaffiliated with a party is greater than the number of registered Republicans or Democrats combined, according to statistics from the Division of Elections.

The last Democratic member of Alaska’s congressional delegation was Mark Begich, Nick Begich’s uncle, who served one term in the United States Senate and lost his 2014 reelection bid.

Alaska’s U.S. senators, both Republicans, Lisa Murkowski and Dan Sullivan, congratulated Ms. Peltola.

Ms. Murkowski said Ms. Peltola “has a long track record of public service to our great state.” Ms. Murkowski and Ms. Peltola were in the state Legislature together.