ANCHORAGE — The race began, fittingly, in the spring season known here as breakup.

As sheets of ice cracked into pieces across the rivers, melting snow exposed the gravel and dust on roads, and preparations began for hunting and fishing, dozens of congressional campaigns were springing to life with barely a few days of planning. Candidates held solemn conversations with their families, advisers hastily secured website domains and the endorsements and donations began flooding in.

The unexpected death in March of Representative Don Young, the Republican who represented Alaska’s sole congressional district for nearly half a century, has given rise to a crowded and raucous race to succeed him. No fewer than four dozen Alaskans — political veterans, gadflies, and even a man legally named Santa Claus — are running to succeed Mr. Young as the lone representative in the House for the state’s 734,000 people.

The list of candidates is sprawling. It includes former Gov. Sarah Palin, who is endorsed by former President Donald J. Trump; Nick Begich III, whose grandfather held the seat before Mr. Young; four Alaska Natives, including one, Tara Sweeney, who served in the Trump administration; Jeff Lowenfels, a retired lawyer and a prolific local gardening columnist; and Mr. Claus, a portly, bearded North Pole councilman and socialist.

“That’s a lot of people to do research on and figure out,” said Morgan Johnson, 25, as her black cat, Edgar, prowled across the counter of her plant shop in Juneau. “I get stuck on one person’s Instagram for an hour — now I have to do that for 48 people.”

Further complicating the picture, four separate elections in five months will determine Mr. Young’s successor. First, the throng of candidates will compete in a primary contest on June 11. The top four finishers will then advance in August to a special election to complete the remainder of Mr. Young’s term. That same August day, the candidates who choose to do so will compete in yet another primary to determine which four advance to the general election. And finally in November, voters will choose a winner to be sworn in in January 2023.

The sheer volume of candidates owes in part to a new electoral system in Alaska, which opens primaries to all comers, regardless of political affiliation. Under the rules, voters can choose one candidate, and the four who draw the most votes then compete in a runoff of sorts, in which voters then rank their choices. The preferences are counted until someone secures a majority.

State officials and advocacy groups are rushing to pull off the rapid-fire contests and ensure that voters understand how the new rules work.

“We’re compressing everything that usually is done in about seven months in 90 days,” said Gail Fenumiai, Alaska’s director of elections, who said her team would mail and process more than 586,000 ballots. “There’s a significant amount of work involved.”

State officials decided to hold the special election by mail, in part because there was not enough time for the necessary hiring and training of more than 2,000 new election workers, as well as testing and sending election equipment across the state. A ballot was carefully designed to fit all the names on one side of paper, with the first ones sent out less than six weeks after Mr. Young died.

Candidates have also had little time to build a campaign that stands out or crisscross a mountainous state where villages and towns are often accessible only by plane or ferry.

“When you’re vying for a limited set of first-round votes, you have to figure out how to put yourself forward in a way that people will hear it and resonate with it,” said Christopher Constant, an Anchorage assemblyman and Democrat who announced his intent to challenge Mr. Young in February.

The broad field has roiled the close-knit political circles here, pitting longtime colleagues and friends against one another.

“This seat has been held for 49 years by one guy, and people are just hungry to have a different voice in Congress, and they think that they can add to it,” said John Coghill, a former state senator who is among the candidates.

It has also cracked the door open for a series of history-making bids, including four candidates who would be the first Alaska Native to represent a state where more than 15 percent of the population identifies as Indigenous.

“It is long past time that an Indigenous person was sent to D.C. to work on behalf of Alaska,” Mary Peltola, a Democrat who spent a decade in the state Legislature and is Yup’ik, said in an interview in Anchorage.

Ms. Peltola is among the candidates who have gone to great lengths to highlight a personal connection or appreciation for Mr. Young.

The fiercest competition is inside the Republican Party, where younger conservatives who had waited their entire lives in Mr. Young’s shadow are contending for the mantle of his successor. The filing deadline was on April 1, two weeks after Mr. Young died, meaning that candidates had to decide whether to run before funeral services for the congressman had concluded.

“It stunned the entire state, and then having to figure out what this new reality was going to look like and what processes were in front of Alaskans with respect to this vacancy — it’s been exhausting,” said Ms. Sweeney, a co-chair of Mr. Young’s campaign and now a candidate for his seat.

Ms. Sweeney, who is Inupiaq and the first Alaska Native woman to serve as assistant secretary for Indian Affairs, has emerged as a leading contender for Republicans, with top Alaska Native-owned corporations banding together to back her campaign.

Mr. Begich, a conservative whose grandfather of the same name held the seat as a Democrat until his disappearance in a plane crash in 1972, angered many in Mr. Young’s inner circle by jumping into the race in October as a challenger, dangling what they saw as insinuations that the congressman was too old.

The chosen candidate of the state Republican Party, Mr. Begich has disavowed the $1 trillion infrastructure bill Mr. Young proudly championed and the congressman’s penchant for earmarking federal dollars for Alaska.

“For too long, the formula in Alaska has been to sacrifice the good of the nation for the good of the state, and I don’t think that that’s a formula that we need to be practicing going forward,” Mr. Begich said in an interview.

Mr. Young’s allies have gravitated toward less conservative candidates.

Those include Ms. Sweeney and Josh Revak, a state senator and an Iraq war veteran who secured a coveted endorsement from Mr. Young’s widow, Anne.

“It was a really difficult choice, but if he believed in me and others believe in me, that I have the heart and the work ethic and the experience to do the job, then I’ll walk through fire to do it,” Mr. Revak, wearing an ivory bolo tie with the Alaska Senate seal and his Purple Heart pin, said after a recent fund-raiser at an Anchorage home.

Ms. Palin’s late entry into the race — and Mr. Trump’s near-immediate endorsement of her — has further scrambled the political picture. As a former governor and vice-presidential candidate, Ms. Palin, whose campaign did not respond to requests for an interview, easily has the strongest name recognition in the field of candidates.

But she has also become a frequent target for candidates in both parties, as her rivals seek to weaponize her visibility in national headlines, stoke the lingering discontent in the state about her abrupt decision to leave the governor’s mansion in 2009 and woo the thousands of voters who have moved to Alaska since.

At a recent event at an airplane hangar in Juneau, Mr. Begich jumped at the opportunity to poke fun at Ms. Palin.

“I take it you’re not going to be on the ‘The Masked Singer,’” one woman remarked to him, as the dozens of people gathered chuckled.

“I don’t have a pink bear costume,” Mr. Begich replied, referring to Ms. Palin’s 2020 appearance on the reality show.

Most observers here believe that Mr. Young’s seat is likely to remain in Republican hands given the state’s conservative slant, but the new ranked-choice system, which tends to advantage candidates in the center, could upend the conventional wisdom.

It could, for instance, help Al Gross, an independent who unsuccessfully challenged Senator Dan Sullivan, a Republican, in 2020. Mr. Gross gained both national attention and some local derision with a viral campaign ad that dubbed him “Alaska’s own bear doctor.”

“Certainly this campaign is not about bears, and it is about Alaska,” Mr. Gross, a former orthopedic surgeon, said in an interview.

Unlike in 2020, when the Senate Democratic campaign arm endorsed him, he vowed to rebuff financial support from any major political party and said he planned to join the Problem Solvers Caucus, a bipartisan group, should he win.

The Alaska Democratic Party has taken aim at him, calling Mr. Gross a “proven loser.”

Republicans have also unleashed a torrent of Christmas-themed attacks against Mr. Claus, a sign that there is at least some concern that the combination of his name recognition and his professed “affinity for Bernie Sanders” could help him prevail in a ranked-choice election. (Mr. Claus, who changed his name nearly two decades ago, often wears red robes of the monk’s order of which he is a member and plans to join the Congressional Cannabis Caucus if elected.)

“Whoever winds up in this special for that term, for the remainder of Don Young’s term, should be concentrating on representing all Alaskans then and there, not running for additional time in office and not spending time raising money or campaigning,” Mr. Claus said, adding that he was seeking only to finish Mr. Young’s term this year.

Citing concerns about the pandemic, Mr. Claus said he was limiting his in-person campaigning and soliciting electoral support virtually from his perch as a North Pole councilman.

But, he added, “I’m taking it seriously.”