Albert Barnes Commentary Jeremiah 38:19

"And Zedekiah the king said unto Jeremiah, I am afraid of the Jews that are fallen away to the Chaldeans, lest they deliver me into their hand, and they mock me." — Jeremiah 38:19 (ASV)

The Jews who have defected to the Chaldeans - These deserters probably formed a numerous party, and now would be all the more indignant with Zedekiah for having rejected their original advice to submit.