PORTLAND, Maine (AP) — The presence of ranked choice voting on the ballot in Maine is a new wrinkle in a state famous for its own Yankee brand of political independence, and could play a role in deciding the presidency.

Voters in the state approved the adoption of ranked choice voting in a 2016 referendum drive. After withstanding numerous legal challenges, the method appears on ballots in a presidential race for the first time in U.S. history this fall.

Maine's vote this year is a test case for whether the system can work elsewhere, said Craig Burnett, a Hofstra University political science professor and ranked choice voting expert.

“This is nice for those proponents to see it in action and say look at the results — it worked,” Burnett said. “Or it didn’t, depending on what your perspective is.”

The potentially lengthy process of counting ranked ballots also has prognosticators wondering if the election could come down to Maine’s four electoral votes. It’s a longshot, and it would take a very close election, but it’s within the realm of possibility, Burnett said.

The method works like this: First, voters can rank the candidates on their ballot in order of preference. If no candidate breaks 50% of the popular vote, the bottom finisher is eliminated, and voters' second choices come into play. The tabulations continue until a candidate achieves a majority of the total votes.

Ranked choice voting arrives on Maine’s presidential ballots in a year when three of the state’s four electoral votes could be in play. The state is one of only two that apportions electoral votes — one each — by congressional district, of which Maine has two. The statewide vote, which is worth two electoral votes, could also be up for grabs.

Neither Republican President Donald Trump nor Democratic nominee Hillary Clinton managed to crack 50% statewide in 2016, although Trump cruised to victory in the state's rural 2nd Congressional District. Most polls show Democratic former Vice President Joe Biden holding a statewide lead this time.

The use of ranked choice voting has become a partisan issue in Maine, where Democrats roundly support it and Republicans have launched a bevy of unsuccessful legal challenges to torpedo it. The state also uses it for Congressional and U.S. Senate seats.

The state first used ranked voting in 2018, when the method propelled Democratic challenger Jared Golden to victory in a congressional race against Republican incumbent Rep. Bruce Poliquin, deepening Maine Republicans’ opposition.

State Republicans, who lost a Maine Supreme Judicial Court ruling in September in their attempt to block ranked voting, have said the method “has caused considerable concern among voters wondering how they can make sure their ballot is not thrown out or invalidated in the counting or retabulation process." It has also criticized the method as confusing.

Maine Democrats, meanwhile, “value elections that are fairer and more inclusive,” and are on board with ranked voting, said party spokesperson Seth Nelson. Supporters of ranked choice voting have also said it eliminates spoilers and encourages voters to be more informed about all the candidates.

Maine’s presidential ballots this year include five candidates — Trump, Biden, Libertarian nominee Jo Jorgensen, Green nominee Howie Hawkins and Alliance nominee Roque “Rocky” De La Fuente. The third party candidates are unlikely to equal the 7% of the votes earned together by Libertarian nominee Gary Johnson and Green nominee Jill Stein in 2016, but their presence on the ballot could be enough to trigger the need for another round of tabulation. That could easily take a week or more of counting.

It's difficult to say whether Trump or Biden would be more likely to benefit from second-choice ballots. And it's also possible many voters won't ranked their choices at all, said Mark Brewer, a political scientist with the University of Maine.

Ranked choice voting is one of a few ways Maine is different from the rest of the Northeast politically. Maine is the only state in New England that currently sends two non-Democrats — independent U.S. Sen. Angus King and Republican U.S. Sen. Susan Collins — to Washington. The method could also play a role in Collins' bid for reelection, as she runs in a closely watched race against Democratic House Speaker Sara Gideon and independents Max Linn and Lisa Savage.

Maine’s 2020 presidential election is the highest-profile use of ranked choice voting in U.S. history, and could help raise the method’s profile in other states, said Rob Richie, president of election reform group FairVote. Ranked choice is currently used in local elections elsewhere in the U.S. It has also been used in other countries, including Ireland and Australia, for decades.

Alaska and Massachusetts are considering ballot initiatives that could adopt ranked voting in future elections — Alaska's initiative would extend ranked voting to presidential elections, while the Massachusetts initiative would not.

“The world is watching,” Richie said. “And I think they will be learning.”