New York City Democrats will choose their nominee for mayor in next week’s primary election. The city uses ranked choice voting, allowing voters to select up to five candidates in order of preference.

Ranked-choice voting could once again decide New York City’s mayoral primary, four years after the process was slow and marred by a major tabulation error.

New York City's mayoral election has become the race to watch because of its surprisingly competitive nature but also the electoral system that's helped it become so competitive: ranked choice voting.