PORTLAND (AP) — Couriers are rolling in Maine to collect ballot materials as the state determines the winner of a U.S. House seat via its new voting method for the first time.

Mainers ranked their choices in Congressional ballots this week in case no candidate cleared 50 percent of the popular vote. The office of the secretary of state says that appears to be the case in the contest between Republican Rep. Bruce Poliquin and Democratic challenger Jared Golden.

The office says couriers were out Thursday and tabulations under the new method will likely begin Friday. The calculations will be open to the public.

Voters’ second choices will come into play to try to determine a clear winner of the hotly contested race.

The announcement of a winner is expected next week.

What is ranked-choice voting?

Instead of selecting a single winner, voters were asked to rank all of the candidates from best to worst on the ballot in a new way of voting approved by state voters.

The election marked the first time what is known as ranked-choice voting was used in U.S. House and Senate races.

The system is used for municipal races in about a dozen cities. But Mainers took it a step further, approving it use in statewide primary elections and federal races in general elections.

Democratic Congressional candidate Jared Golden, left, autographs a campaign sign as he and his supporters wait for elections results in the 2nd Congressional District election, Tuesday, Nov. 6, 2018, in Lewiston, Maine. (AP Photo/Joel Page)

Why is Maine using ranked choice voting?

The history of ranked-choice voting in Maine dates to 2001, when a lawmaker introduced a bill to create it.

The idea gained support — with the largest city, Portland, adopting the system for mayoral races in 2010 — but it was unsuccessful statewide until 2016, when Maine voters OK’d the system by ballot referendum.

Nine of the past 11 gubernatorial elections had resulted in winners who failed to get a majority of the vote. Electoral reform group Fair Vote and the Texas-based nonprofit Action Now Initiative have provided hundreds of thousands of dollars to bring ranked-choice voting to Maine.

In May 2017, Maine’s high court advised that parts of the ranked-choice voting law are unconstitutional when it comes to state general elections. Supporters pressed to use the system in primaries and federal races.

Lawmakers tried to block the rollout by requiring a constitutional amendment by December 2021, but voters approved a second statewide referendum nullifying the legislative delay.

How does this system work?

Voters rank candidates from first to last on their ballot, and the election is over if one candidate wins a majority of first-place votes. If not, candidates are eliminated one by one and their votes reallocated in what amounts to a mathematical game of survival.

The eventual winner might not be the candidate who had the most first-place votes, but rather the one who tallies the highest number of second- or even third-place votes.

Voters can also simply fill in one oval with their first-choice candidate. Or they can fill in multiple ovals to rank all of the candidates.

Rep. Bruce Poliquin greets supporters and speaks with the press at Dysart’s Travel Stop in Bangor on Tuesday, at what they hoped would be a re-election party. (Michael G. Seamans/Morning Sentinel)

When will Maine know its ranked winners?

It could take some time in the 2nd Congressional District, the most expensive race in state history and the only one for which neither candidate collected a majority.

Democratic Secretary of State Matthew Dunlap said the results of additional rounds of ranked-choice tabulations won’t be known until sometime next week.

Dunlap said a courier service has been contracted to begin retrieving the results from town clerks on Thursday. The office isn’t committing to a day in which the unofficial voting outcome will be announced but said it will likely be next week.

What are the benefits?

Advocates say it helps promote civility, end election spoilers and ensure the eventual winner receives majority support.

Supporters also say the system avoids the cost of a separate runoff election and encourages collaboration among candidates.

Some proponents have pointed to Republican Gov. Paul LePage’s election in 2010 with 38.1 percent of votes in a five-way race.

What are the drawbacks?

Critics say ranked-choice is confusing and leads to bland campaigns in which candidates steer clear of contentious topics because they don’t want to alienate any voters.

Jason McDaniel, associate political science professor at San Francisco State University, says his research shows ranked-choice voting increases the rate of ballot errors and disqualifies ballots, particularly among lower-income residents.

Associated Press writers David Sharp and Marina Villeneuve contributed to this report.