Deeply unpopular among Democrats and Republicans. A Democratic challenger who could unite ethnic voting blocks--Hasidim and Asians, especially--alongside Manhattan, Williamsburg, and Long Island City/Astoria Whites would trounce Adams in a primary. The question is--who could that candidate be, if anyone? I would be most curious to see an AOC run, but someone like Nadler might better fit the bill. I doubt either would like to leave their congressional run in favor of the mayorship, however.
Hasidm are almost certainly going to vote for the Republican barring something odd happening (like bribery).
Bribery wouldn't be something odd. It's how Hasidic politics works.