New York Mayor Bill de Blasio has announced his run for the presidency, the latest Democrat to enter the race.
In a video released on Thursday, Mr de Blasio said it was “time we put working people first” and that President Donald Trump “must be stopped”.
“I’m a New Yorker, I’ve known Trump’s a bully for a long time,” he added. “I know how to take him on.”
He is expected to visit Iowa and South Carolina to begin campaigning this weekend.
Mr de Blasio is the 24th person to run for the Democratic presidential nomination in 2020.
The Manhattan-born politician beat eight other Democratic contenders in his mayoral primary.
The 58-year-old progressive won a landslide victory in 2013 to become New York’s first Democratic mayor since 1993.
Previously serving as a senior figure on the city’s council, Mr de Blasio has implemented a programme of free universal pre-school, made police wear body cameras and highlighted economic inequality in the most populous city in the US.
In 2017 he was re-elected in another landslide, winning more than 66% of the vote against his Republican challenger.
But rumours he would announce a run for the presidency failed to energise the city.
An April Quinnipiac poll said 76% of New Yorkers did not want him to stand.
“Every listed party, gender, racial, borough and age group agrees that the mayor should not hit the campaign trail,” the pollster reported.
His campaign was rocky even at pre-launch stage. His press secretary resigned, as did a communications aide to the mayor’s political action committee (PAC).
And news of Mr de Blasio’s planned Iowa campaign event on Friday was first reported on Twitter by a high school journalist, who took a screenshot of a since-deleted Facebook event page that misspelt his name.
As he prepared for a morning talk show interview with his wife, Chirlane McCray, on Thursday protesters chanted “liar” outside the ABC News studios in Manhattan.
“A little serenade,” he laughed, during the live interview with Good Morning America.
It is not clear what provoked the protest but in 2016, Mr de Blasio was fined nearly $48,000 (£37,500) by the New York City Campaign Finance Board for multiple spending violations in his first mayoral race.
Mr de Blasio has regularly criticised Mr Trump on immigration, policing and climate change.
He held an event at the base of Trump Tower in May calling on all the president’s businesses to cut their emissions in line with New York’s Green New Deal legislation – a package of environmental laws.
“You’re on notice, Donald: we won’t let you mortgage our future for your real estate,” the mayor later tweeted.
This prompted a Twitter battle with President Trump’s son, Eric, who called the rally “simply childish”. The president retweeted some of his son’s attacks.
Mr de Blasio has officially changed his name twice in the past.
Born Warren Wilhelm Jr, he changed it in 1983 to Warren de Blasio-Wilhelm, court records show.
Then in 2001, he petitioned a Brooklyn judge to change it to Bill de Blasio, saying he was taking his mother’s maiden name because his father had been largely absent from his childhood and he identified with her Italian heritage.