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 said 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 Democrat's presidential nomination in 2020.
But the Manhattan-born politician is no stranger to crowded races, beating out eight other Democratic contenders in his mayoral primary.
The 58-year-old progressive politician 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.
Mr de Blasio was elected by a landslide in 2013, securing more than 73% of the vote
But rumours he would announce a run for the presidency have angered 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 before it even began. His press secretary resigned as news of a potential run broke - as did a communications aide to Mr de Blasio's Political Action Committee (PAC).
And news of the mayor'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 which misspelt Mr de Blasio's name.
He held an event at the base of Trump Tower in May calling on all Trump 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 in the building "simply childish". The president retweeted some of his son's attacks.