As votes were counted on Tuesday night, Brooklyn Borough President Eric Adams, a former police captain who co-founded a leadership group for Black officers, was in a tight race with former city sanitation commissioner Kathryn Garcia and former de Blasio administration lawyer Maya Wiley.
Former presidential candidate Andrew Yang, who was far behind in early returns, conceded about two hours after polls closed and vowed to work with the next mayor.
But with the debut of the ranked voting system and a mountain of absentee ballots still at least a week away from being counted, it could be July before a winner emerges in the Democratic contest.
In the Republican primary, Guardian Angels founder Curtis Sliwa defeated businessman Fernando Mateo. Ranked choice voting wasn't a factor because there were only two candidates in the race.
Check here for NYC Primary Results NOTE: Ranked Choice Voting data will be published June 29th when released by the NYC Board of Elections
For the Democrats with 13 candidates, voters ranked up to five candidates, from first to last, on their ballot.
If one candidate is the first choice of a majority of voters - more than 50% - that person would have won the race outright, just like in a traditional election.
Because nobody hit that threshold, ranked choice analysis kicks in.
Vote tabulation is done in rounds, and in each round, the candidate in last place is eliminated.
Votes cast ranking that candidate first are then redistributed to those voters' second choices.
The process repeats until there are only two candidates left, and the one with the most votes wins.
THE KEY DATES
June 22, 2021 Unofficial results at close of polls will include first choice votes from early voting and election day
June 28, 2021 Canvass begins for absentee and affidavit ballots
June 29, 2021 Preliminary RCV round by round elimination will not include absentee and affidavit ballots (Report 1)
June 29, 2021 Last day for the Board to receive an absentee ballot
July 6, 2021 Preliminary RCV round by round elimination (Report 2)
All rounds of counting are done by computer in a process that takes very little time, but absentee ballots complicate things.
Because of the ongoing coronavirus pandemic, all people in New York were allowed to vote by mail.
Mail ballots had to be cast by Tuesday but could take several days to arrive, and a complete ranked choice analysis can't be done until those ballots are included.
More than 87,000 absentee ballots had been received by the city as of Monday, with more expected to arrive in the mail over the next few days.
Besides Adams, Garcia, Wiley and Yang, other contenders in the Democratic contest included City Comptroller Scott Stringer, former U.S. Secretary of Housing and Urban Development Shaun Donovan, former Citigroup executive Ray McGuire and nonprofit executive Dianne Morales.
Stringer, McGuire and Morales addressed supporters after polls closed as early returns showed them trailing the front-runners but did not immediately concede.
Next Tuesday, on June 29, the Board of Elections will run its first ranked choice analysis, using only votes cast in person. Results will be posted on the board's website.
They will show who the winner and runner-up would be if no votes had been cast by mail.
RELATED | NYC elections: What is ranked choice voting?
A week after that, on July 6, the board will do another round of ranked choice analysis that includes all of the absentee ballots processed as of that date.
If there are still uncounted or disputed ballots, the process will be run yet again on July 13, and every subsequent Tuesday until a winner can be declared.
Current Mayor Bill de Blasio, a Democrat, leaves office at the end of the year due to term limits.
(The Associated Press contributed to this report)
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