TRENTON, N.J. — The confrontation was brief but explosive, and it laid bare the deepening fault lines within the Democratic Party in one of America’s bluest states.

New Jersey state troopers singled out Sue Altman, the leader of the left-leaning Working Families Alliance, grabbed her by the arms and forcibly removed her from a standing-room-only State Senate hearing on corporate tax breaks.

She was led past her main political rival, George E. Norcross III, a Democratic power broker who was at the hearing to testify in support of an $11 billion economic incentive program that Ms. Altman had criticized harshly and that is the subject of state investigations and subpoenas.

The imagery and its aftermath have roiled Trenton, exposing a generational and philosophical rift between progressive and mainstream Democrats that is mirrored nationwide.