PORTLAND — Mayoral candidate Ethan Strimling received the endorsement Monday of former state representative John Eder, one of Strimling’s 14 opponents for the city’s first popularly elected mayor’s position in 88 years.

Eder, one of the race’s two Green Independent Party candidates, is the first candidate to throw his support behind one of his opponents. He will remain on the ballot, however, because they’ve already been printed.

Eder said he wasn’t conceding the race. But he said his chances to win were “slipping,” and told his supporters they should put Strimling either No. 1 or No. 2 on their ranked-choice ballots.

“We represent a new guard fighting against the status quo,” Eder said of him and Strimling. “We need new leadership.”

The duo held an 11 a.m. press conference near an undeveloped Bayside field at the corner of Chestnut and Somerset streets. Throughout the race, Eder has advocated providing a tax break to private developers for simple and affordable housing in that area.

Eder has said the city needs to entice private developers to build reasonably priced housing for workers who don’t qualify for subsidized housing and who work, shop and contribute to the downtown area.

Strimling called Eder’s plan a “great idea,” and said he will pursue it if elected Nov. 8. But he stressed that Eder didn’t ask for anything before giving the endorsement.

“This is big a help,” Strimling said. “From the business community to the Greens, we’re building a big umbrella, a big tent. … And that’s what we need in City Hall, someone who can bring constituencies together.”

Eder said the fact that Strimling is willing to embrace others’ ideas — including his own — led to the endorsement. Eder has also talked about organizing local businesses into small co-ops to take advantage of pieces of the Affordable Health Care for America Act that will take effect in 2014.

Strimling said Eder’s focus on affordable health care and affordable housing will help bring people and jobs to the city.

Strimling’s style meshes “with my idea of being an activist,” Eder said, “because I can work from the outside and I know I have Ethan’s ear because he’s willing to listen to all good ideas, even if they’re not his own.”

The endorsement comes only days after Strimling submitted his first campaign-finance report of the year, which showed he had raised more than $83,300. That was $37,000 more than current City Councilor and incumbent Mayor Nick Mavodones, who raised $47,000, the second highest total of the 15 candidates.

Strimling also had more than $26,000 on hand on Oct. 25, according to the report, far more than any other candidate.

The endorsement comes as somewhat of a surprise because of Eder’s background. Eder helped mentor City Councilor David Marshall, the other Green Independent Party candidate running for mayor.

But Eder said Marshall is already on the City Council and “doing great work,” and the city needs fresh leadership. He said with Marshall still there, and Strimling as mayor and Eder advocating from the outside, “we’re going to make a great team for this city.”

Terry Bouricius, a former senior policy analyst for FairVote: The Center for Democracy and Voting, a nonprofit organization in Maryland, said these sorts of endorsements are typical in large ranked-choice voting elections.

Bouricius, who’s studied ranked-choice elections across the country, said during typical plurality elections, which Portland previously used, candidates with like-minded ideas see each other as threats and tend to attack each other.

But in ranked-choice elections, it doesn’t hurt candidates if someone with like-minded ideas is ranked second on a voter’s ballot. So joint campaigning often happens, he said.

“Quite frankly, it’s logical for candidates — if they really care for the city — to promote candidates who are politically and idealogically like them,” Bouricius said. “These joint press event, where they say ‘If you like me, rank me first and him second, and if you like him, rank him first and me second,’ makes perfect sense.’”

Eder agreed, and said he expects more candidates to start endorsing each other as Nov. 8 closes in.

Fellow candidate Michael Brennan said he’d heard about discussions between Eder and Strimling last week, and wouldn’t be surprised if more candidates began endorsing each other. But he predicted these endorsements’ effects on the race would be “minimal.”

Brennan said he hasn’t had discussions with other candidates about them endorsing him.

Mavodones said “these are the back-room type deals that turn people off about politics.” “But the voters are smart,” he added. “I think they are paying attention.”

Several of the other candidates, including Jed Rathband, praised Eder for the specific ideas he brought to the race, but Rathband said Eder’s endorsement was misguided.

“John has brought a lot to this race,” Rathband said. “But if it’s new leadership he’s looking for, (he and others) might want to consider what I bring to the race: A fresh perspective not beholden to anyone at City Hall, a plan with real economic development opportunities, and that’s why I’ve gotten the support of Portland Community Chamber’s political action committee.”