Here's how it would work: In races with more than two candidates, "instead of selecting a single candidate, each voter ranks all the candidates in order of preference," Marsha Mercer reports for Stateline. "If no candidate is the top choice of the majority of voters, the candidate with the fewest first-place votes is scratched from every ballot, and there is a second count. This time, on every ballot where the last-place candidate was ranked first, the second-ranked candidate is counted as the voter’s top choice. The counts continue until one candidate is the top remaining choice of a majority of voters."
Proponents of ranked-choice voting "ran a $2 million campaign facing no organized opposition," Shepherd writes. "They pitched the new voting method as a cure for the kinds of plurality elections that have decided nine out of the last 11 gubernatorial races, including Republican Paul LePage’s wins in 2010 and 2014," where he received less than 50 percent of the vote. "It was the polarizing LePage who provided the petri dish" for the experiment. The Maine League of Women Voters endorsed the idea.
The remaining obstacles to ranked-choice voting are "based on concerns, including from Maine Attorney General Janet Mills, that it doesn’t pass constitutional muster." The state constitution specifically allows election by plurality, and says ballots must be received, sorted and counted by cities and towns. Ranked-choice voting would be handled by the secretary of state.