Ranked voting will decide a pivotal congressional race. How does that work?

AUGUSTA, Maine — In a pivotal congressional race in Maine, the state's ranked choice voting system is being used to determine the winner, but that won't be the end of it. The currently trailing candidate has requested a full recount that won't begin until after more than 12,000 votes have been reallocated to determine a majority.

Election workers will try to complete both tasks quickly enough to ensure the results are certified and sent to the governor by Maine's Nov. 25 deadline, though state law grants an exception for recounts.

Why so much attention to this race?

The contest between Democratic Rep. Jared Golden and Republican challenger Austin Theriault in Maine's second congressional district is one of a dwindling number of uncalled races that will determine which party controls the U.S. House.

The race is between a Marine Corps veteran incumbent who sometimes bucks his fellow Democrats and a stock car driver who supports conservative values but has fashioned himself as a potential unifier in Congress.

The race drew plenty of attention and money, upward of $30 million, a large sum for a rural congressional district.

There were fewer than 20 races left to be called to determine control of the House on Monday, after Democrat April McClain Delaney narrowly won a district in Maryland and Republican David Schweikert won reelection in Arizona on Sunday.

What is ranked choice voting?

Ranked choice voting, adopted by Maine voters in 2016, allows each voter to rank their lesser choices.

If no candidate wins a majority of first-place votes, then other rounds of tabulations begin, reallocating the lesser choices of the last-place finisher's supporters, until one candidate has a majority.

Golden is familiar with the process. An additional round was needed to declare him the winner when he unseated Republican U.S. Rep. Bruce Poliquin in 2018, and again in a rematch in 2022. The first time, Poliquin had the most first-place votes but Golden emerged with a majority after second choices were added. Golden had the most first-place votes in their rematch, and again came out on top.

As the counting got underway on Tuesday, Secretary of State Shenna Bellows explained the process — which she said would take most of the week — to a room crowded with media, lawyers and other representatives from the campaigns as well as hundreds more watching a livestream on her department's YouTube page.

To reassure observers that they could have faith in the results, she described how chain-of-custody was preserved, through sealed envelopes, locks and secret codes in some cases, all watched over by law enforcement as the ballots were moved from polling places to the room where they were being opened and retabulated Tuesday in the state capital of Augusta.

''That strict chain of custody is very important for everyone involved in the election, that's why we're doing things here in full view of all of you and everyone watching on the livestream,'' Bellows explained after ballots in locked blue boxes were wheeled in from a secure room by a team including an armed detective.

She said the workers — with lawyers for both campaigns eyeballing the tapes — first verify the totals from each polling place. Only then do they run the ranked choice voting tabulation, "so that second choices for people who did not choose Golden or Theriault are folding up into the count, and as a result we'll know, between those two, who has 50%," Bellows said.

What are the next steps?

Golden claimed he won the vote outright after some media organizations declared him the winner, but the secretary of state's office then announced that the ranked-choice process was necessary because neither candidate had surpassed 50% for a first-round victory.

All of the ballots were then transported from sites across the 2nd Congressional District to a building in Augusta that houses the Maine Emergency Management Agency and the Maine Department of Safety.

Starting Tuesday, election workers began scanning the thousands of individual ballots into a computer. Once that's completed, the ranked tabulation takes only seconds with a stroke of a computer keyboard. Officials hope it's completed by week's end.

But the process doesn't end there. Before the ranked choice process was announced, Theriault requested a recount that will likely take more than a week to complete.

How close is the race?

The Associated Press has not declared a winner. Both candidates received slightly less than 49% of first-choice votes, with Golden ahead by about 2,000 votes, according to figures released by the secretary of state.

It's so close that it could come down to second choices of voters who supported the one declared write-in candidate, retiree Diana Merenda, who collected 400 votes, and more than 12,000 ballots that were left blank. The ranked choice tabulation will account for whether any of those blanks included a second or third pick despite having no first-place choice.

Any ballots that are truly blank — with no candidates chosen — will not be counted. Ballots with undeclared write-in candidates won't be counted, either.