New Yorkers have passed a ballot measure implementing ranked-choice voting in primary and special elections — a dramatic shift that could have big implications for future elections.

Under a ranked-choice system, voters can rank up to five candidates in order of preference. If no single candidate wins a majority of the vote, the candidate with the least number of votes is eliminated and the votes for that person are redistributed to the voters’ next preferred candidate. That process of elimination continues until one candidate clinches a majority. Voters can rank anywhere between one and five candidates.

New York’s new voting system was approved with more than 73% of the vote and will be implemented in 2021. The adoption of ranked-choice voting in the biggest city in the country is a signal the system could catch on across America in coming years.

Proponents of ranked-choice voting cite a host of benefits the system offers. They argue the system will eliminate the risks of less popular “spoiler” candidates who benefit in crowded races when their opponents split the vote. And it will get rid of costly runoff elections, while encouraging more candidates to run and, as a result, more voters to get to the polls.

They also point to evidence that candidates will shy away from attacking their opponents, particularly those whose supporters they believe overlap with their own, because they’re motivated to appeal to a broad swath of the electorate. And they cite studies that show that more women and people of color run under ranked-choice voting, in part because of the reduction in negative campaigning.

The system is already in use in nearly 20 other American cities, including San Francisco, Santa Fe, and Minneapolis. Maine is expanding ranked-choice voting to the 2020 presidential election. But New York is by far the most populous area to approve ranked-choice voting and will triple the number of people across the country who vote this way.

The plurality voting system, also called “first-past-the-post” or “winner takes all,” is used by most of the US. Ranked-choice voting is used in democratic elections around the world, including in Australia’s legislative elections, the UK’s mayoral elections, and Ireland’s parliamentary, presidential, and local elections.

However, some Democrats and many Republicans take issue with ranked-choice voting. Critics say the system can confuse voters and make ballot counting more complicated. Some are concerned about “ballot exhaustion,” which occurs when voters’ don’t rank all of the candidates, including those that make it to the final round of ballot counting. This means they ultimately don’t have a voice in choosing between the two most popular candidates.