(CNN) Maine voters will conduct a groundbreaking democratic experiment on Tuesday when they use, for the first time in the nation, ranked choice voting in statewide primaries.
The consequences of Maine's experiment could be momentous, with the potential to change campaigns, enliven third-party candidacies, and if successful, serve as proof-of-concept for the system at scale.
The system was adopted through a voter referendum in 2016 and has survived a series of legal challenges in the intervening years, while emerging as a flashpoint in the state's politics.
Here's how it works, according to the Committee for Ranked Choice Voting, which helped campaign for the referendum:
"Ranked choice voting gives you the power to rank candidates from your favorite to your least favorite. On Election Night, all the ballots are counted for voters' first choices. If one candidate receives an outright majority, he or she wins. If no candidate receives a majority, the candidate with the fewest first choices is eliminated and voters who liked that candidate the best have their ballots instantly counted for their second choice. This process repeats and last-place candidates lose until one candidate reaches a majority and wins. Your vote counts for your second choice only if your first choice has been eliminated."
Maine's Secretary of State has provided a series of materials for voter education ahead of primary day, including a video walkthrough and a series of online FAQs and explainers.
The original ranked choice voting referendum passed 52% to 48% in 2016, with "yes" votes coming mostly in the Democratic regions of the state, and "no" votes coming largely from Republican areas. The path to implementation, however, was quickly derailed amid concerns over the system's constitutionality and the feasibility of its use.
The legal conflict ricocheted through the state courts, ultimately landing before the state Supreme Court, which ruled in April that the system could go forward. On primary day, Mainers will also vote on whether to use the system for federal congressional races in November.
Maine Democrats have largely been supportive of the system, while state Republicans have been largely opposed.
Ranked choice voting has been implemented for some local elections, notably in Portland, Santa Fe, New Mexico, San Francisco and Oakland, California, and Minneapolis, Minnesota. Advocates of the system would like to see it expand.
Rob Richie, president and CEO of FairVote, an organization that advocates for ranked choice voting, said politicians are resistant because they fear unintended consequences or losing knowledge of the rules of the game.
"It actually has an interesting impact, campaigns really change," Richie said. "The simple fact is that you need to talk to more people to get their vote as a second or third choice, and the way you target those votes changes. There's no one you won't have a conversation with."
"These are things that change the nature of the game in a good way, but incumbents are used to running in a certain way, and it seems to make them nervous," he said.
Richie recalled the initial resistance when ranked choice voting was implemented in Santa Fe.
"With Santa Fe, implementation was tough. The clerk didn't want it. Now, everyone is very happy with it," Richie said. "The city had to be sued to do it, they ultimately did, and I think the general impression is that it made things better."
The Santa Fe city clerk and public information officer did praise the system in a report following implementation there.
"Fears [about the system] proved largely unfounded," they reported, saying the system "resulted in clear and transparent outcomes, markedly high turnout, and little-to-no issues across two early voting centers and twelve Election Day sites."
In an interview with CNN, Jason Savage, executive director of the Maine Republican Party, made clear his party's opposition to the new system.
"We don't like the process, we don't like the methodology, it doesn't deliver a majority -- you only have to get a majority of what remains after multiple rounds," Savage said. "People were promised one thing and handed something dramatically different."
Savage also suggested that the referendum was the result of undue influence by out-of-state groups.
"It's driven by some big national money, and activist groups in Maine got excited because they don't like our governor, Paul LePage," he said.
Maine's current governor is certainly part of the equation. LePage was elected and reelected governor with a plurality in three-way races.
Phil Bartlett, chair of the Maine Democratic Party, acknowledged that frustration at the results of the last two gubernatorial elections was a factor in the successful 2016 referendum.
"LePage's original election in 2010, he won with 38% --- that certainly created a lot of interest,' he said. "But momentum just keeps building."
Bartlett also rejected the notion that Maine was being used as ground zero for national voting reform. "Look at Portland, [Maine], they implemented ranked choice voting and have had two successful mayoral elections. There's been lot of grassroots support for ranked choice voting for a long time in Maine."