Adams definitely could lose the Democratic Primary if any Democrat in the Congressional Delegation (even AOC) decided to challenge him.
Someone like Grace Meng or Dan Goldman would win easily, and I think Adriano Espaillat would also win a head-to-head primary against Adams. (In fact the only Democrat in the City's delegation who wouldn't win is Hakeem Jeffries, largely because I doubt he'd run as the sitting House Minority Leader.)
I'm not convinced any of them would beat Adams, and AOC would be crushed.
