The developers of the Down Island Golf Club turned up the heat on the Martha's Vineyard Commission last night, hammering home the threat of a large low-income housing project if the golf club plan is not approved.

"This commission is in a position to vote yes on a golf course or yes on a housing development. There is no real ‘no' available here," said Brian Lafferty, a partner of developer Corey Kupersmith, who has filed an alternate plan for a 366-unit housing project on some 274 acres owned by Mr. Kupersmith.

The housing plan is the subject of a court dispute that is expected to test whether the MVC has the right to review Chapter 40B housing projects.

In an undisguised attempt to raise the stakes in the golf course campaign, Mr. Lafferty told the commission last night that the state attorney general had filed a motion in Massachusetts Land Court court yesterday morning to intervene on behalf of the developers.

It was not the only surprise announcement as the clock wound down on the fourth public hearing on the golf course project. The project is under review by the commission as a development of regional impact (DRI). This is the second DRI review for Mr. Kupersmith, whose first golf club plan was reject by the commission last year.

Mr. Kupersmith, who has not attended the public hearings this time around, also submitted two letters to the commission demolishing any notion that he might consider some future sale of his land to a conservation group.

"Since we have not discussed the sale of my property to the land bank for many, many months, now, I would not consider such a conservation sale," Mr. Kupersmith wrote in a letter to land bank executive director James Lengyel that was sent to the MVC.

In a separate letter to the Sheriff's Meadow Foundation, Mr. Kupersmith wrote: "I will never sell my land to a conservation group."

Last night the long-running hearing on the golf course plan got a little longer when the commission decided to continue the hearing to a fifth session. The final session is now set for Jan 3.

Mr. Kupersmith wants to build a Rees-Jones-designed 18-hole golf course on his property, with a full-service clubhouse and dormitory housing for employees. He has proposed an organic turf-management plan. He has also proposed a hefty "community benefit" package to sweeten the deal, including payments to the town in lieu of taxes and monetary gifts to an array of local charities, including Island Elderly Housing and the ice rink.

Again last night, much of the testimony focused on the housing threat.

"Looming in the background is a project that would destroy the fabric and the nature of this town. An applicant for 366 houses is a hostile applicant in our view," declared Michael Dutton, chairman of the town board of selectmen.

"I have to think very long and hard about the potential impact of a 40B application - it would be the demise of our town," said Oak Bluffs selectman Richard Combra in an impassioned plea.

Oak Bluffs resident Theo Nix said the MVC approval of a golf course in Edgartown two years ago should translate to a similar approval in Oak Bluffs. "What's good for Edgartown is good for Oak Bluffs," declared Mr. Nix.

Opponents of the golf club also turned out out in force. Rick Bausman, an Edgartown resident and conservation advocate, presented the commission with a petition with 700 signatures opposing the golf course.

Mark Nelson, a hydrogeologist with Horsely and Witten, testified as a paid expert for the Vineyard Conservation Society. Mr. Nelson said the developer had lowballed nitrogen loading calculations for the Lagoon Pond by failing to use widely accepted standards used by the state and the Cape Cod Commission.

Jeffrey Bernstein, an environmental attorney who also works for VCS, told the commission that the golf course fails the commission's well-known benefits and detriments test. Among other things, Mr. Bernstein said, the golf course plan does not comply with the southern woodlands district of critical planning concern (DCPC) regulations.

Mr. Bernstein presented the commission with the recent state Natural Heritage and Endangered Species Program biomap which designates the southern woodlands as a core habitat for wildlife.

Rob Culbert, an Island wildlife biologist, later amplified the core habitat issue, describing the southern woodlands as an important interior forest habitat for wildlife, including the scarlet tanager and the box turtle.

Mr. Bernstein urged the MVC to not be diverted by the housing threat. "With all due respect, I think it's a red herring - your evaluation should be based on comparing a range of facts, not with a sword hanging over your head," he said.

There was also simple testimony from Island residents both for and against the project.

"I am speaking for the local people, the fishermen and shellfishermen and other working people," said Nelson Smith, a lifelong Island resident whose family goes back for generations. "This Island is a place of unique natural beauty, of clay cliffs and salt ponds. Highly manicured landscapes like golf courses - that is what we consider to be off-Island," he said.