India, June 25 -- New York City is using ranked choice voting in itsDemocratic mayoral primary election taking place Tuesday, June 24. The system allows voters to rankcandidates in order of preference rather than pick just one.

Those who support ranked choice voting believe it builds consensus, promotes positive campaigning and allows voters to express a fuller range of opinions. Opponents, however, believe the system is too complicated and could lead to ballots being thrown out.

In this system, the number of candidates a voter can rank depends on the specific rules in an area. In New York City, as many as five candidates can be ranked in one race.

Voters, however, are not required to fill their ballots. A voter who supports only one c...