PORTLAND, Maine (AP) Total spending in advance of a fall referendum about a hydropower transmission corridor in western Maine has surpassed $40 million as groups on both sides of the issue continue to spend money.

Energy companies contributed more than $6.8 million to groups on either side of the Central Maine Power corridor campaign over the past three months, the Bangor Daily News reported. Spending in favor of the corridor is still ahead of spending against the project.

The project would bring hydropower from Quebec into western Maine to connect to the New England power grid. Construction already has begun but a November referendum aims to stop the project.

Wrangling over the $1 billion New England Clean Energy Connect has gone on for years. The Maine Supreme Judicial Court ruled last year that a different citizens’ initiative designed to block the power project violated the Maine Constitution.