BAR HARBOR – The citizen group MDI Tomorrow plans to co-sponsor a public forum next month to hear both supporters and opponents of the Nov. 2 property tax cap referendum.

The group got support this week from all four municipal managers on the island, representing Bar Harbor, Mount Desert, Southwest Harbor and Tremont, who agreed to co-sponsor the forum.

Bar Harbor Town Manager Dana Reed said the forum must present both sides of the property tax debate and not only the side that opposes it.

Reed recently told his own council that Bar Harbor stands to lose up to $4 million under the tax cap proposal, under the worst-case scenario. The town and school would each suffer an estimated $2 million funding loss, he said.

Reed said municipalities in Maine are likely to raise revenue through fees to offset some of the financial loss.

Meanwhile, Town Manager Michael MacDonald of Mount Desert said selectmen will not only have to revisit the controversial issue of whether to charge a sewer user fee, but consider fees on other services, should the referendum pass.

Mount Desert would lose about $1.2 million in property tax revenue under the proposal. The best case scenario shows an $800,000 reduction in property taxation.

Reed, during a Tuesday meeting of the MDI League of Towns, also questioned whether professional town staff should express an opinion either way on the tax-cut referendum.

Mount Desert Selectman Patrick Smallidge argued that the professional managers should be able to tell residents what the impact of the measure would be on towns and schools.

Smallidge emphasized that residents should be told about the effect of the measure on local control and the time-honored New England tradition of town meeting government.

“Without that kind of input, the forum is useless,” he said.

Stephanie Clement, a leader in the MDI Tomorrow citizen group, approached the MDI League of Towns on Tuesday to ask that the towns co-sponsor the forum.

She said MDI Tomorrow wants to remain neutral on the question.

“MDI Tomorrow is really all about process, facilitating discussions and providing facts so people can figure out for themselves which way they want to go,” Clement said Friday.

The forum will be held either on Oct. 13 or Oct. 27, possibly at Mount Desert Island Regional High School, which could accommodate a crowd, she said.

Noel Musson, an MDI Tomorrow volunteer, and state Rep. Ted Koffman, D-Bar Harbor, are organizing the forum, Clement said.