New York City's first mayoral primary decided by ranked-choice voting chose a front-runner who led in every round, even after a protracted count marred by a reporting error. In Maine, Democrat Jared Golden trailed in the first round of a 2018 ranked-choice congressional contest but defeated the GOP incumbent in the next round.

Now, Minneapolis' mayoral and City Council races are set to once again use the fiercely debated system. While the November election marks its fourth citywide ranked-choice election, the method is gaining momentum around the country.

"This allows people to vote with their hearts and their heads," said Susan Lerner, executive director of Common Cause/New York and board chair of the pro-ranked-choice group Rank the Vote NYC. "They don't need to pick the lesser of two evils."

But resistance to the system remains deep.

"It takes away from the one person, one vote," Maine state Rep. MaryAnne Kinney said. The Republican said she believes the voting system is "extremely confusing."

Minneapolis Mayor Jacob Frey used the system to his advantage four years ago, when the one-term City Council member soundly defeated Mayor Betsy Hodges. Now Frey is fighting for his political life as he faces 16 challengers, including several who are banding together to use intricacies of the system to try to block the embattled mayor from a second term.

Ten years ago, Minneapolis was one of only 10 cities across the United States that had adopted ranked-choice voting, according to FairVote, a leading advocate of the method. That number has now risen to more than 40 cities, according to the organization, which touted on its website that New York City's contest was the "largest city-wide RCV election in American history."

While voting in New York City ended June 22, it took two weeks for a winner to be called in the city's hotly contested Democratic mayoral primary. A reporting error in late June involving test ballots led to the NYC Board of Elections issuing a statement that ranked-choice voting "was not the problem, rather a human error."

The Associated Press called the race for Eric Adams on July 6. Despite the delay and tumult, the election had the city's highest turnout for a citywide primary in more than two decades, according to the NYC Campaign Finance Board. But in the aftermath, the divide over the electoral system hasn't subsided.

Lerner said ranked choice is helping reshape the city's male-dominated politics by boosting the number of women who are Democratic nominees for council seats, most being women of color.

For critics, the June contest only heightened their opposition. Weeks before the primary, New York City Council Member I. Daneek Miller pushed for letting voters decide whether to continue using ranked-choice voting for city government's primary and special elections.

"We have said from the very beginning that ranked-choice voting threatened to undermine the voting power of communities of color, and that successful implementation of a new voting system during a global pandemic was impossible," Miller, a Democrat and co-chair of the New York City Council's Black, Latino, and Asian Caucus, said in a statement last week. "When we finally got the cast-vote records back from the Board of Elections, the data does show an uneven education process and a clear difference between communities that most heavily utilized ranked-choice voting versus those that did not."

Minneapolis residents voted overwhelmingly in 2006 to adopt ranked-choice voting, then referred to as an instant runoff election. At the time, supporters said they hoped the change would minimize the chances of a resident's vote being "wasted" and encourage more positive campaigning. Critics said they feared it would cause confusion and reduce debate by eliminating primary elections.

In Maine, ranked-choice voting is used for state and federal primary elections, along with general election races for federal offices, according to the Secretary of State's Office.

First used in 2018, the system came under intense scrutiny later that year when the Democratic challenger Golden toppled incumbent Republican U.S. Rep. Bruce Poliquin. Despite Poliquin's narrow lead in the first round of the general election results, Golden won the seat after third-party candidates were eliminated.

"Ranked-choice voting improves representation because it gives voters true choices," Maine Secretary of State Shenna Bellows said. A vocal supporter of the method, Bellows said she thinks "ranked-choice voting has achieved exactly what we hoped here in our state. It's empowered voters to vote on their principles rather than party politics."

While ranked choice is gaining momentum, the shift has faced setbacks. Last year, Massachusetts voters rejected a statewide ballot question on ranked-choice voting. The system has gained a foothold in other parts of Minnesota. St. Paul began using the method locally in 2011, while ranked choice was used for the first time in St. Louis Park in 2019 for City Council elections. Voters in Minnetonka and Bloomington signed off on using the voting method last year.

In other pockets of the country, ranked choice is more familiar. In California, the system is used in San Francisco elections for choosing many local offices, according to the city's website, with Oakland and Berkeley also serving as early examples of the method being put in place out West.

In another major upcoming test of the system, Alaska is working to implement ranked-choice voting for the 2022 general election in state and federal races. Voters narrowly approved the change last November as part of a larger ballot measure that also includes a nonpartisan open primary system.

"The hope with ranked-choice voting and open primaries is that you get people who are much more focused, and much more worried, about policy issues as opposed to political problems," said Jason Grenn, executive director of the pro-ranked-choice group Alaskans for Better Elections, who served one term in the Alaska House as an independent.

Asked about ranked-choice voting as he left the U.S. Senate floor one night, Alaska GOP Sen. Dan Sullivan said that he didn't support the measure, adding that "nobody understood it."

"To be honest, a lot of people in Alaska are confused," Sullivan said.

Staff writer Liz Navratil contributed to this report.