A left-wing candidate has pulled up from behind to become the dark horse in New York City's Democratic mayoral primary. His surprise success is indicative of the debate raging within the Democratic Party on what kinds of leaders they want in the Trump era.

After Donald Trump's stunning 2024 presidential victory - where he made inroads in reliably liberal New York City - a millennial New York state assemblyman had a question.

"What would it take for you to vote for a Democrat in the future?" Zohran Mamdani asked Bronx and Queens residents who either swung for Trump or didn't vote.

The query was part of a video series that went viral and helped make the 33-year-old democratic socialist - with little name recognition - into a serious contender for New York City's mayor.

Democrats in New York head to the polls on Tuesday to choose a nominee to lead American's biggest city. Nine people are vying for the job, in a race that could have implications for the party nationally as it tries to take on Trump.