Schlossberg, 33, was defeated by assemblymember Micah Lasher in a crowded race to succeed congressman Jerry Nadler. Lasher was an aide to Nadler.
Schlossberg, the son of Caroline Kennedy, is a Vogue correspondent, Harvard Law School graduate and political newcomer known for his quirky social media posts.
Another also-ran in the 12th district was George Conway, the conservative lawyer who set up an anti-Trump group, the Lincoln Project. He managed to win only about 6% of the vote.
Mamdani made no endorsement in that race.
The mayor said earlier on Tuesday: “It’s not just a question of electing more Democrats. It’s a question of electing better Democrats.
“When I look at these candidacies, I see in them a willingness to also put working people back at the heart of our politics.”
But establishment Democrats in Washington are concerned that the left-wing candidates might not appeal to swing voters in this November’s midterm elections.
All three candidates backed by Mamdani have vowed to “abolish ICE” and “tax the rich”, and they have accused Israel of genocide, which it denies.
Hakeem Jeffries, the Democratic leader of the House of Representatives, said of Mamdani: “We have agreed to strongly disagree.
“A handful of primaries that go in one direction or the other, in a given state or two, aren’t going to reshape who we are as House Democrats.”
