Brooklyn Councilman Chi Osse joined the Democratic Socialists of America earlier this year, making him the fourth City Council member on the rolls of the left-wing group, which has become increasingly influential amid the rise of mayoral front-runner Zohran Mamdani.
Osse, a friend to Mamdani who’s at 27 the youngest member of the Council, confirmed to the Daily News on Tuesday that he has joined the DSA’s New York City chapter, but wouldn’t immediately say when he became a dues-paying member.
Two sources in the group said Chi joined shortly after June’s Democratic mayoral primary, which Mamdani, a longtime DSA member, won by a nearly 13% margin over ex-Gov. Andrew Cuomo.
The revelation of Chi’s DSA membership comes on the heels of an Axios report that he has been considering launching a 2026 primary challenge against Congressman Hakeem Jeffries, the Democratic Party’s minority leader in the U.S. House of Representatives. Chi has neither confirmed nor denied that he’s mulling such a run.
The DSA’s standing as a force in city politics has surged since Mamdani shocked the political establishment with his Democratic mayoral primary win. Mamdani’s polling as the favorite to win next month’s general mayoral election, facing off again against Cuomo, who’s running as an independent this time around, and Republican nominee Curtis Sliwa.
Zohran Mamdani. (Barry Williams / New York Daily News)
The DSA has long been a sharp counterpoint to centrist Democrats, who fear lawmakers with leftist views could be used by Republicans to paint the entire party as ideologically extreme.
DSA members and their supporters have long argued the opposite, saying their proposals, like tax hikes on the wealthy and expanded social programs, are widely popular with the party’s rank-and-file and should be embraced by all Democrats.
Leftist groups and lawmakers have been especially energized since President Trump’s 2024 election, which they view as an indication of that the Democratic Party’s middle-of-the-road leadership is failing.
Perhaps the DSA’s biggest star, New York Rep. Alexandria Ocasio-Cortez, has this year embarked on a nationwide “Fighting Oligarchy” tour with Vermont Sen. Bernie Sanders to present an alternative vision for the Democratic Party.
At a major campaign rally in Manhattan on Monday night, Mamdani hinted at the internal ideological battle, saying his mayoral campaign created “a movement that won the battle over the soul of the Democratic Party.”
“We are not afraid of our own ideas,” Mamdani said to a crowd of over 3,000 supporters in a pointed jab at the party’s more moderate elements.
Councilmember Chi Osse attends a City Council meeting. (Adam Gray/AP)
Osse, who represents parts of Bedstuy and Crown Heights in the Council, first hinted at his DSA membership at the same rally, where he was among a lineup of speakers introducing Mamdani.
“If you want this movement to continue, you guys got to join New York City DSA,” Chi said without mentioning he recently joined the group.
Since his 2021 election, Osse has been a vocal proponent of progressive policies.
But he also used to keep the DSA at arm’s length, including specifying on social media in 2023 that he wasn’t supported by the group during his first campaign after an online critic lambasted a statement he had put out about the war between Israel and Hamas.
The other three City Council members on the DSA rolls are Tiffany Caban of Queens, Alexa Aviles of Brooklyn and Shahana Hanif of Brooklyn.
In addition to Mamdani, who’s currently an Assemblyman representing northwestern Queens, the DSA also counts eight New York State lawmakers as members.
Originally Published: October 14, 2025 at 11:24 AM EDT