Jamaal Bowman Lost. Is Another Squad Member Next?

On Tuesday, Representative Jamaal Bowman became the first member of the Squad — the group of like-minded progressive House members — to lose a congressional election. The former middle-school principal was ousted by Democratic challenger Westchester County executive George Latimer, who won by a double-digit margin in the most expensive House primary ever.

Bowman’s troubles can’t be attributed to one thing. His pro-Palestinian stance...