PORTLAND — Portland officials said today they may try to hold a special election following a city council vote on Monday that effectively rejected $19.6 million in state aid to build a new middle school.

State Education Commissioner Susan Gendron said today that the city has until Sept. 12 to hold a successful referendum or it will lose the money.

City officials had planned to hold a referendum on the school project on June 10, but the measure failed to win seven council votes necessary to support borrowing the money.

The council voted 6-3 on a proposal to build the school where the former Baxter Elementary School stands off Ocean Avenue. It would replace the Clifford Elementary School, which would close. The Maine Department of Education would reimburse the city.

Mayor Edward Suslovic and councilors David Marshall and Kevin Donoghue opposed the project.