American Priorities, which started just six months ago, has quickly emerged as an influential force in House Democratic primaries, spending at least $5.6 million to boost Democrats who are fiercely critical of Israel. It helped democratic socialist Melat Kiros defeat Colorado Rep. Diana DeGette on Tuesday.

In recent primaries, New York Democrats have shown the powerful lobby group the door

American Priorities, which started just six months ago, has quickly emerged as an influential force in House Democratic primaries, spending at least $5.6 million to boost…