The five-member Democratic majority on the Fairfax County Board of Supervisors voted yesterday with rare party discipline to hold public hearings on the controversial Springfield Bypass one week before Virginia's gubernatorial election.

The board's four Republican members objected, charging that the hearings were intended to embarrass J. Marshall Coleman, the GOP's gubernatorial nominee. Coleman, Virginia's state attorney general, has been the target of Democratic attacks because he refused to disqualify himself from investigating the actions one of his fund-raisers took in winning state approval of the road's path across Fairfax.

The state selection of that route for the $200 million highway last month angered the board and led to conflict-of-interest allegations against Coleman supporter William B. Wrench, a member of the state highway commission, who owns property along the route. Following The Washington Post's disclosure of Wrench's property, he resigned under pressure from Coleman and Gov. John N. Dalton.

Members of Democratic gubernatorial candidate Charles S. Robb's campaign and Robb himself were in touch with several Fairfax supervisors before yesterday's vote, which promises to keep the proposed cross-county highway before the public through late October.

Democratic supervisors said they simply want the public to have more of a say on where the road should go, but Fairfax Board Chairman John F. Herrity, a Republican, said: "There's no doubt it's become a partisan issue."

The board, which has unanimously opposed the state's route for the highway, agreed yesterday to ask both Coleman and Robb to state their position on the best alignment for the road. Republican Herrity brushed aside suggestions that the move could hurt Coleman, since Robb has already come out in support of a county-supported route.

"If Marshall Coleman doesn't intend to support the voters of Fairfax County then the voters ought to know about it," Herrity said. "I don't give a damn whether it helps him or hurts him. That's not my problem. I'm representing the people of Fairfax County here."

The state route would carry the bypass near two business parcels and a vacant lot owned by Wrench. It would also place half of an interstate cloverleaf on a 387-acre tract owned by Wrench's lawyer John T. (Til) Hazel Jr., and his partner Milton V. Peterson, who also owns land along the county route.

Wrench, Hazel and Peterson all serve on Coleman's finance campaign committee, leading to Democratic charges that Coleman could not fairly investigate Wrench. Coleman rejected those attacks and later ruled that Wrench had violated the spirit of state conflict-of-interest laws by voting on the alignment.

Last week the highway commission, operating without a Northern Virginia representative, reaffirmed its route selection, angering Fairfax officials. They then argued the county should retaliate by holding more hearings on the issue, in part to keep pressure on state officials.

"We have had discussions with the state, we tried to have negotiations and they were not terribly interested in that, and now I think it's time to hear from the public," Democratic Supervisor Audrey Moore said yesterday.

Robb also has called for public hearings, and his campaign manager confirmed yesterday that he had discussed the issue with several Democratic supervisors during the past week. Robb himself talked during the weekend with Democratic Supervisor Joseph Alexander, who earlier opposed a public hearing on the highway.

Alexander said after the vote that he had discussed transportation issues with Robb, but not the bypass. He said he changed his mind because of the state's unwillingness to compromise, not the upcoming election.

"I'm damn tired of having those people dictate to us, and we're the ones who suffer," Alexander said. "All this governor did, as far as I'm concerned, is make Mr. Wrench the scapegoat and make him resign."

Republican supervisors countered that the hearings would not change the state's position. "What are we going to do in terms of meeting the citizens' concerns when the highway department is turning a deaf ear?" said Republican Supervisor Nancy Falck. "Are we falsely raising expectations?"

The Democrats responded that after the hearings the county could put its alignments on a regional transportation plan, thereby discouraging the federal government from providing funds for the state route. Melvin Deale, assistant federal highway administrator for Virginia, said the government could fund a route not on the regional plan, but "it would be messy, it would be controversial, it would be a battle."