If Portland residents vote Tuesday to expand the use of ranked-choice voting in local elections, they could be asked to take action again before an unanticipated wrinkle creates problems in the 2022 school board election.

That’s because two at-large seats on the Board of Public Education will be on the 2022 ballot, and those seats are currently awarded to the two candidates who get the most votes. But under Portland’s ranked-choice voting rules, there can be only one winner because a candidate has to get more than 50 percent of the votes cast to be elected. That means additional rules or another charter amendment would likely be needed.

City Clerk Katherine Jones said Friday that she would need to do additional research before providing an answer a question about how ranked-choice voting would be used in multi-seat races such as the at-large school board race.

Anna Kellar, spokesperson for Fair Elections Portland, which is advocating on behalf of expanding ranked-choice voting in Portland, said the group only became aware of the issue recently. Kellar stressed that councilors will have two years to address the problem, whether through rules or an additional charter amendment.

“There are ways to do it,” Kellar said. “This isn’t going to cause any sort of calamities. We just have to decide what method we use.”

The proposal to expand ranked-choice voting to all City Council and School Board races in Portland was drafted by Fair Elections Portland. But the group did not secure the required number of signatures to place it on the November ballot, so councilors, citing community support for the measure, placed it on the March 3 ballot on the group’s behalf.

Ranked-choice voting has been used in the city’s mayoral election since 2011.

In a ranked-choice election, voters rank the candidates in order of preference. If no candidate gets more than 50 percent of the first-choice votes, the last-place candidate is eliminated and his or her ballots are redistributed to the other candidates based on the second or third choices. That instant-runoff process continues until one candidate gets more than 50 percent of the votes.

The process should work as expected in nearly all City Council and school board races. The exception is one at-large contest for two seats on the school board that takes places once every three years. It’s also possible that it could be an issue if the council or school board has an at-large vacancy that is filled in an election already featuring another at-large race.

Kellar said Fair Elections Portland has consulted with FairVote, a nonprofit that advocates for ranked-choice elections nationwide.

FairVote recommends setting a 33 percent-plus-one threshold for a two-seat race, according to its website. That threshold is intended to be “the smallest number which guarantees that no more candidates can reach the threshold than the number of seats being filled.”

“Multi-winner RCV is a fair representation voting system, meaning it gives like-minded voters the chance to win legislative seats in proportion to their share of the population,” FairVote says on its website.

The group also says winners of two-seat races can be determined by conducting the instant run-off until only two candidates remain, or by conducting a repeat runoff, which would elect one winner on the first instant runoff and select the other winner through a second runoff that would exclude the first winner, Kellar said.

Either method would require some sort of council action and perhaps another charter amendment, since the city’s current charter says the winner of a ranked-choice election needs to receive a majority of the vote. The current charter is silent on multi-seat races, though it does contain a provision that says “the city clerk may adopt additional regulations consistent with this subsection to implement these provisions.”

Expanding ranked-choice voting is the only question on the municipal ballot. But also voters will be heading to the polls to cast ballots in the presidential primary and a statewide effort to overturn a bill enacted last year removing philosophical and religious exemptions from vaccinations.

The success of the ranked-choice voting initiative hinges not only on whether it receives a plurality of support. It also depends on voter turnout, which should be aided by the presidential primary and the people’s veto.

At least 30 percent of city voters who cast ballots in the previous gubernatorial election need to cast ballots on the charter amendment for it to be valid. That means at least 9,982 voters need to cast a municipal ballot for the charter amendment to take effect, said Jones, the city clerk.

City Councilor Justin Costa, who helped advance Fair Elections Portland’s proposal, said he expects the council to do whatever is necessary to ensure that the voting method can be used in all races, including the 2022 school board race.

“I think if this is the way people want to go and that creates some sort of issue, I would be shocked if we don’t take it up quickly and deal with it,” Costa said.