Members of the Dorchester-based Boston Teachers Union this week voted in support of breaking away from the Greater Boston Labor Council, a union umbrella group with 100,000 members.

The teachers union has more than 8,000 members, making it the largest city of Boston union. The split, if finalized, would mean the Greater Boston Labor Council (GBLC) would no longer receive BTU dues, and could no longer count the BTU as part of its membership.

The GBLC’s website lists Jessica Tang, the BTU’s leader since 2017, as its vice president. Tang was among the union leaders contacted by the Reporter on Friday and she declined to comment.

The exact reasons behind the potential break were not immediately clear on Friday. Union leaders in both camps declined to comment.

But discussions have been underway focused on expanding the number of GLBC leadership positions, potentially diluting BTU’s power within the umbrella union.

The potential split also comes as a municipal election cycle gets going, with City Council seats on the ballot. Unions have clashed behind the scenes in past election cycles over the various endorsements. Candidates covet union endorsements when they come with support in the form of campaign cash and union members who can knock doors and pull voters to the polls.

The vote to authorize a split came Wednesday, when BTU members gathered at the teachers union’s Mount Vernon Street headquarters as part of their regular membership meeting.

There are still additional procedural steps before the BTU-GBLC split could be finalized, and there is a chance for the reconciliation between the two camps.

The BTU vote did not affect its affiliation with the American Federation of Teachers (AFT) of Massachusetts, which represents teachers from pre-kindergarten to 12th grade, school support staff, libraries and higher education educators.

The GBLC’s executive board includes representatives from pipefitters union, Boston Firefighters Local 718, the Massachusetts Nurses Association, machinists union, Greater Boston Building Trades Unions, IBEW Local 103, SEIU 509, the Teamsters and 32BJ SEIU, among others.