Supporters and opponents of a proposed expansion of ranked-choice voting in Maine presented conflicting arguments to the state’s high court Wednesday on whether applying the system to gubernatorial and legislative races would be constitutional.

Arguing in favor of the expansion were attorneys for Maine’s Democratic legislative leaders and the nonpartisan League of Women Voters of Maine. The Office of the Maine Attorney General and the Republican National Committee urged the justices to reject the expansion.

The Maine Supreme Judicial Court was asked by lawmakers to weigh in as the Legislature considers a bill to expand ranked-choice voting. No action was taken Wednesday, and Chief Justice Valerie Stanfill said the justices would issue an opinion at a later date.

The justices, hearing arguments at the Cumberland County Courthouse in Portland, seemed skeptical of arguments in favor of the expansion, and questioned whether they should even be taking up the issue.

At one point, Justice Andrew Mead asked whether the debate constituted something new, or if it was just a rehashing of a 2017 case in which the court found that ranked-choice voting could not be used in state-level races. (The method is currently used only in state primaries and federal races.)

The reasoning behind the 2017 decision is that the Maine Constitution says the winners of state races must be determined by a plurality, or whoever gets the most votes.

“Is this a whole new animal coming to us, or is it a reboot of what happened in 2017?” Mead asked.

Peter Brann, an attorney for Maine Senate President Mattie Daughtry and House Speaker Ryan Fecteau, said the question now before the court seeks to further clarify the issues.

He argued that the 2017 case was “only the opinion of the justices at the time” and that the court should reevaluate questions about ranked-choice voting now that the state has experience having used it. (The 2017 case occurred before Maine’s first application of ranked-choice voting in 2018.)

Brann acknowledged the constitution requires winners in state elections to be determined by a plurality, but said it also gives the Legislature the power to oversee how votes are counted. “You put those two together, and we find this is constitutional,” he said.

Assistant Attorney General Jonathan Bolton argued, meanwhile, that it’s clear a plurality is determined after the first round in ranked-choice voting.

“(Ranked-choice voting) inherently produces a plurality winner after round one, which is the first choice of the voters of Maine in terms of who they want to hold that office,” Bolton said. “It’s as simple as that.”

The justices challenged Bolton on whether the Legislature has discretion in determining what a vote is and how elections are carried out.

He said the constitution is clear on requiring that municipal officials be able to quantify in their election returns the number of votes for each candidate. “That can only be done if a vote is the first-choice vote,” he said.

Lawmakers are seeking the court’s opinion in response to LD 1666, which would extend ranked-choice voting to the state’s gubernatorial and legislative races. If the court says the proposal is constitutional, it could pave the way for major changes ahead of this election season.

Ranked-choice voting, first adopted in Maine via a 2016 citizen referendum, allows voters to rank candidates in races featuring three or more contenders in order of preference.

If no candidate gets more than 50% support in the first round, then the last-place finisher is eliminated, the second-choice votes of that candidate’s supporters are reallocated to the remaining candidates, and the results are retabulated. The process repeats until a winning candidate receives more than 50% support.

In addition to potential use in legislative races this fall, the system — if expanded — could have major implications in the governor’s race, which is likely to feature at least one independent.