The legal showdown over whether Minneapolis can go ahead with ranked-choice voting for city elections this fall reached the Minnesota Supreme Court on Wednesday.

Justices signaled that although they find the vote-counting method confusing, especially for multiple-seat elections, they're not sure there's a constitutional flaw in the law. They pressed the law's challengers repeatedly on that point.

Ranked-choice voting -- known in some jurisdictions as instant runoff voting -- was approved handily by voters in 2006. It allows voters to rank candidates in the order they prefer them. In single-seat elections, if no candidate gets a majority of first-choice votes, the candidate with the fewest votes is eliminated, and his or her votes are reallocated to the surviving candidates, based on the second-choice preferences listed on those ballots. The process is repeated until one candidate gets a majority.

A trial court early this year rejected a challenge by the Minnesota Voters Alliance, which argued that the method violates voter rights.

The Supreme Court expedited its review of that decision. The city told the court it needs a decision by June 11 in order to decide whether to abort plans for ranked-choice voting this year. If it drops ranked-choice voting, the City Council by law must state its reasons.

Given the uncertainty posed by the legal challenge, the city is on a two-track system that proceeds as though the new method will be used, but keeps the option of using the traditional primary-general election method if there is a snag.

Arguing for the challengers, lawyer Erick Kaardal argued that there is a constitutional requirement that the outcome of an election reflect voter intent. He argued that the ranked-choice counting method can sometimes mean a voter's second or third choice can thwart the voter's first-preference if it helps a lower-ranked candidate get elected.

He also argued the court's 94-year-old precedent in a Duluth city election case bars the city's approach.

But several justices and City Attorney Susan Segal noted a key difference between how Duluth counted votes and the Minneapolis method. Duluth added second-choice votes to first-choice votes if a candidate's first-choice votes were not sufficient to be elected. But Minneapolis counts the second-choice votes of only those voters whose first-choice candidates were mathematically eliminated. So each voter gets only one vote, they said.

Justices struggled to grasp the mechanics of how votes would be counted for multi-seat elections, such as electing three at-large park commissioners. Now, voters vote for three candidates equally; under the new system, they would list three choices in order of preference. There is then a complex system of counting votes that involves rounds of dropping candidates who mathematically can't hit the threshold for election, and distributing the second-choice votes of voters who voted for the eliminated candidates.

That is supplemented by redistributing to other candidates fractions of surplus votes achieved by candidates who hit the election threshold.

A report is due to be given to the City Council a week from Wednesday on a mock ranked-choice voting exercise conducted this month to test city procedures. Steve Brandt • 612-673-4438