Why did Maine voters approve ranked-choice voting?

It was close — 52 percent in favor to 48 percent against. But a slim majority seemed to want reform, and ranked-choice voting had been successful in two mayoral races in Portland. This year’s measure was put into motion in 2014, but the campaign coincided with rising voter anger over Maine’s governor, Paul R. LePage, a Republican, who has repeatedly embarrassed the state with contentious comments. Mr. LePage was twice elected in three-way races with less than a majority of the vote, which may have given voters an added incentive to approve this measure. The state Democratic Party supported it, though ranked-choice voting does not favor one party or another, and it earned the support of the League of Women Voters of Maine. One major concern was that ranked voting violates the state’s Constitution, which calls for elections of the governor and Legislature by a plurality, not a majority, but a constitutional amendment could resolve that.

How much will it cost?

In Maine, the secretary of state’s office said it would need $761,000 in fiscal year 2017-2018 and $641,000 in fiscal year 2018-2019 to print additional ballot pages and update ballot machines. The Department of Public Safety said it would need a general fund appropriation of $76,000 and a highway fund allocation of $73,000 in fiscal years 2017-2018 and 2018-2019 for overtime and fuel to retrieve, secure and return ballots for central counting in Augusta, the state capital.

How has it worked elsewhere?

Ranked-choice voting is used in Ireland and Australia in national elections, and it is used to pick the Oscar nominees for best picture. But only 11 American cities, all of them liberal, have instituted it, so their experience may be too limited to draw firm conclusions.

Here in the United States, it generally appears to be working. But there is some question about whether it decreases turnout; some studies say it has, others say that when compared with the current system in most cities, it has not. A study of the 2014 mayoral primary in Minneapolis found that voters who were more affluent and white turned out at a higher rate and completed their ballots more accurately than minorities and those in low-income areas.

Howard Dean, a Democrat and former governor of Vermont, favors ranked voting, saying that without a majority vote, “you can’t hold the powerful accountable.” But Gov. Jerry Brown of California, also a Democrat, vetoed a bill in September that would have expanded it in a number of jurisdictions. He called ranked voting “overly complicated and confusing.”

Ranked voting has certainly led to some unexpected results. In the mayor’s race in Oakland, Calif., in 2010, Jean Quan, who came in second in the initial round, had also strategically campaigned to be everyone’s second or third choice. In subsequent rounds, she surged to victory on the strength of those second- and third-place votes after other candidates were eliminated. Supporters of the candidate who had come in first in the initial round accused Ms. Quan of gaming the system.

Why have only cities adopted this method until now?

Ranked-choice voting has been easier in cities because they have uniform voting equipment and are geographically compact, reducing issues involving the central counting of ballots.