AUGUSTA — In a highly unusual move, the Maine Senate voted Monday to authorize its president to seek intervenor status in a case in Kennebec County Superior Court that could decide whether ranked-choice voting will be used in the June primaries.

The 21-13 vote late in the day gives Republican Senate President Michael Thibodeau permission to ask the court to hear the chamber’s concerns about the 2016 ballot-box law that gave Maine the first-in-the-nation, statewide ranked-choice voting system.

On Friday, Kennebec County Superior Court Justice Michaela Murphy heard arguments from attorneys representing the Committee for Ranked Choice Voting, which backed the ballot measure and wants Secretary of State Matthew Dunlap to implement ranked choice for the June 12 primaries. Murphy said Friday that she would decide quickly, noting voters are entitled to clarity about how the primaries would be handled.

Dunlap’s attorneys also said they welcomed Murphy making the call so they could move forward with a ranked-choice primary.

But on Monday, Thibodeau, R-Winterport, outlined the intervenor order, which highlighted new issues with the ranked-choice law that he said were just coming to light as Murphy considered the case. Thibodeau said he could have asked to intervene in the case without Senate approval but wanted its backing because he believed it was the right thing to do.

Sen. Michael Carpenter, D-Houlton, a former Maine attorney general, said the vote was unprecedented and he did not believe the Senate would have standing before the court.

“As important as we think we are, we are not the legislative branch of government,” Carpenter said. “We are a slim majority of one half of a branch of government. I maybe missed something in law school but I think we need to have something more than we have here for us to be legitimately before the court.” Carpenter said he hoped the court would find the state Senate does not have standing in the matter.

But Sen. Roger Katz, R-Augusta, also an attorney, said earlier he believed Thibodeau could have standing. He said the state Senate has a duty to protect the state constitution and that many believe the ranked-choice voting law violates the constitution, which states that election winners are determined by a plurality of votes, not by a clear majority, as would be the case under ranked choice.

In a traditional election, whoever gets the most votes wins, whether a majority or plurality – which can be less than 50 percent. Under the ranked-choice system, voters select candidates in order of preference. If no candidate receives more than 50 percent of the vote, the candidate with the fewest first-choice votes is eliminated. Voters who preferred the eliminated candidate would then have their ballots added to the totals of their second-ranked candidates, and the ballots would be retabulated. The process continues until one candidate has a clear majority.

Katz said the Maine Constitution is based on Massachusetts’ constitution, which was written by President John Adams.

“He became a key voice for the proposition that this whole new experiment of democracy would only work if people had absolute confidence in the integrity of our election system,” Katz said. Some have questioned whether Maine’s election system would retain its integrity under ranked choice, he said. In addition, he said, there are other practical problems with the system, including whether funding is in place for Dunlap to effectively carry out a ranked-choice election in June.

But opponents of having the Senate enter the court case said Republicans were cherry-picking parts of the state constitution while ignoring others that allow citizens to pass laws through the referendum process.

In 2017, the Legislature passed a law that would have delayed and eventually repealed ranked choice, but supporters gathered enough signatures to put that repeal to a statewide vote in June.

Sen. Shenna Bellows, D-Manchester, appealed to her colleagues to consider the will of the voters.

“Our power does not supersede the power of the people,” Bellows said. “The people have spoken. They have said that ranked-choice voting is their will. This body, against some of our objections, voted to amend the law to delay and repeal the will of the people. And the people rose up and they spoke again.”

Senate Minority Leader Troy Jackson, D-Allagash, said the Legislature had ample opportunity to fix flaws in the ranked-choice law and didn’t. He said the Senate majority was using the court to address a policy disagreement and that the order approved Monday was a bad precedent.

“It gives legislative leadership free rein to employ this tactic in the face of any disagreement or policy debate, preventing any type of compromise going forward,” Jackson said. “Lawmakers had the opportunity to make this right last year and implement the will of the voters, but obstructionist legislative Republicans stood in the way once again. And it’s becoming a disturbing pattern of the Legislature, ignoring the will of the people and the referendum results.”

But Thibodeau said he feared chaos would erupt following the June primary if candidates who believed they had been harmed by an unconstitutional law began to file lawsuits. He and others have argued legal challenges and other concerns could delay determining who wins a primary for weeks or months, undermining the stability of government.

“If we don’t get this matter settled, we are headed for chaos in our election system, and that is a huge disservice to the people of Maine,” Thibodeau said.

Maine Senate President Michael Thibodeau, R-Winterport