Edward Doherty, the head of the 6,000-member Boston Teachers Union, has said he will challenge Mayor Raymond Flynn as a candidate in the fall election.
Mr. Doherty, 46, confirmed his rumored candidacy earlier this month, but told reporters that he could still pull out if he does not draw sufficient support.
The union president has said that the Mayor should be held accountable for the "dismal" condition of the city's schools, and charged that Mr. Flynn has withheld sufficient funding because the system is 80 percent minority students.
In recent months, the Mayor proposed abolishing the elected School Committee and placing the schools directly underal control.
Matthew Prophet, superintendent of Portland's public schools since 1982, has said he probably will resign his position next year to take a job in the private sector.
Mr. Prophet, 60, has asked the city school board not to extend his five-year contract, which expires in June 1992.