Here’s how a controversial voting system will decide a congressional race in Maine

For the first time in U.S. history, a controversial voting system known as “ranked choice” is being used to decide a federal election.

It’s happening in Maine, which adopted the system in 2016.

Rather than marking a single candidate, each voter ranks them all, assigning a first-place vote, a second-place vote and so on down the ballot.

If no candidate receives more than 50% of the vote, the lowest-ranked one is eliminated and the results are recalculated. The process is repeated until one candidate exceeds 50%.

In Maine’s 2nd Congressional District, a rural area north of Portland that backed Donald Trump in 2016 and President Obama in 2012, none of the four candidates on the ballot got that majority. Bruce Poliquin, the Republican incumbent, was narrowly leading Jared Golden, a Democratic state representative, 46.2% to 45.5%.

Maine Secretary of State Matthew Dunlap said Thursday that the instant runoff process had started and that he expected a winner to be announced next week. The congressional district is the largest east of the Mississippi River in terms of land area, and private couriers contracted by the state were picking up memory sticks as well as paper ballots from towns that still count votes by hand.

“It’s been a tortured, long journey with ranked choice,” Dunlap said in an interview. “Now it’s going to get a little longer.”

Maine is the only state to adopt the voting system, though several cities in California and across the country use it in local elections. It is similar in some sense to the runoff elections used in some states — mostly in the South — when a candidate fails to win a majority of the total vote.

Proponents say that ranked choice prevents candidates from winning office through a strategy of divide and conquer.

Maine has long had an independent streak, creating a political climate in which ballots are usually filled with independents and third-party candidates. Before the narrow passage of the ballot measure that established the new voting system, nine of the previous 11 gubernatorial elections were won by candidates who had failed to get a majority of the vote.

Rich Robinson, a director at the nonprofit FairVote, said the process “is a win-win solution that gives voters more power and more voice.”

“It provides a way out of gridlock and marginalizes extremism by ensuring more voters matter and upholding majority rule,” he said.

But opponents of ranked choice say it violates laws in Maine and other states where “plurality” provisions specify that the candidate with the most votes wins, even without a majority.

Last year in Maine, the Republican-controlled state Senate asked the state Supreme Court for a nonbinding opinion on whether the system contradicted the state constitution.

The justices concluded that general elections for governor and state Legislature could not be conducted by ranked-choice voting because of a plurality provision, and as a result the state did not use ranked choice in Tuesday’s election for governor.

But because there are no plurality provisions for federal races, the justices did not find any issue with applying ranked-choice voting to those elections.

Gov. Paul LePage, a Republican who secured his office in 2010 with 38% of the vote, told local media in June that ranked choice is “the most horrific thing in the world” and that he sides with people who raise questions about its constitutionality.

Republicans in Maine have been especially critical of the system. Many of the independent candidates or those from minor parties tend to be from the left, and so when they are eliminated, their supporters tend to favor Democrats.

Poliquin, who is vying for a third term and is among the last Republican members of Congress from New England, refused on multiple occasions during the campaign to say whether he would accept the results if ranked choice were to kick in, hinting that he may file a lawsuit to challenge the results if he loses.

The two independent candidates in the race — Tiffany Bond and William Hoar — support gun-control regulations and other causes on the left. Together, they won less than 9% of the vote. But the voters who made them their first-choice candidates will now have a deciding hand in the election.

Ten cities, including Minneapolis and San Francisco, use ranked-choice voting for local elections, according to the National Conference of State Legislatures.

In 2010, the 9th Circuit Court of Appeals upheld up a lower court’s ruling that ranked voting in San Francisco did not violate the constitutional rights of voters.

kurtis.lee@latimes.com

Twitter: @kurtisalee