Two union leaders and longtime Democratic National Committee members have resigned from the national party, marking the latest internal dispute of chairman Ken Martin’s tenure.

Randi Weingarten, head of one of the nation’s most influential teachers unions, and Lee Saunders, the president of a large union of public workers, each pointed to Ken Martin’s leadership.

Randi Weingarten of the American Federation of Teachers and Lee Saunders of AFSCME, declined offers to stay on. Weingarten cited disagreements with Martin.