NEW YORK (AP) -- New York City voters used to picking one candidate per race may soon be marking their ballots for up to five.
  
A measure on the city's ballot Tuesday will let voters rank their choices in primaries and special elections for mayor, city comptroller, public advocate, borough president and City Council starting in 2021.
  
The system is known as ranked-choice or instant-runoff voting. It is in effect in U.S. cities including San Francisco, Minneapolis and Cambridge, Massachusetts, as well as Maine.
  
Backers say ranked-choice voting forces candidates to broaden their appeal beyond a narrow base in hopes of being chosen second or third by voters whose favorite is someone else.
  
Critics of the system call it unconstitutional or confusing.

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