Fairfax County, having lost its battle over the route of the proposed Springfield Bypass to the Virginia state highway commission, now is in danger of losing its representation on the commission itself.

John F. Herrity, chairman of the Fairfax County Board of Supervisors, called a press conference yesterday to urge Gov. John N. Dalton to appoint a Fairfax resident to replace William B. Wrench of Springfield on the commission. Wrench resigned Sept. 18 after disclosures that he owned property along the state-favored route of the $200 million cross-county highway.

Herrity was apparently responding to reports that a former Prince William County supervisor is a leading candidate to replace Wrench, who, like four of the five previous Northern Virginia representatives on the powerful commission, lived in Fairfax.

A spokesman for Dalton, who is at a governors' conference in Puerto Rico, said yesterday the Republican executive might appoint someone from outside Fairfax, the most populous jurisdiction of the 13-county highway district. And the spokesman hinted that the appointment might come in part because of anger at the way Herrity and other Fairfax officials have injected the Springfield Bypass into the current gubernatorial campaign, putting Republican candidate J. Marshall Coleman in a difficult position.

"Some people are very burned up about the whole thing," said Dalton spokesman Charles J. Davis III. "For Jack Herrity or anyone else to attempt to dictate to the highway commission is both misleading, I think, and totally inappropriate."

"I can't remember the last time anyone dictated to the highway commission," Herrity responded. "The highway commission is the dictator."

Asked whether Dalton is so fed up with Fairfax politics that he might look elsewhere for a commissioner, Davis said: "I don't want to speculate on whether the issue at hand has been so politicized in the county as to make the selection of someone objective impossible if that person came from the county."

Prince William officials are pushing Andrew J. Donnelly, a former supervisor who is now a Democrat-turned-Republican stockbroker. "We feel he'd do a fine job," said Prince William County Board Chairman Kathleen Seefeldt. "Some of the issues are so sensitive there in Fairfax . . . any good candidate from Prince William might have a better chance."

Fairfax officials oppose Donnelly, both because they would lose some access to the highway commission and because he might press for construction of a road that Fairfax has long opposed. That road would carry Prince William commuters across the Occoquan River through relatively undeveloped southern Fairfax.

Herrity yesterday suggested Harriet F. Bradley as a possible appointee. Bradley, whom Herrity said would be the first woman to serve on the commission, represented the McLean area on the Fairfax board of supervisors from 1964 through 1971.

Dalton, Coleman and Herrity are all Republicans, and they all support Coleman's bid to replace Dalton, who legally cannot run for a third term. Since disclosures about Wrench's property three weeks ago -- embarrassing to Coleman because Wrench served on his campaign finance committee -- the three have disagreed on the best way to handle the Springfield Bypass issue.

Herrity privately urged the governor to persuade his 10-member highway commission to reopen negotiations over the highway's alignment. Dalton, eager to see the issue resolved before the Nov. 3 election, declined, and the highway commission reaffirmed its support for the route that Wrench originally recommended and the county opposed.

Herrity has persuaded his fellow supervisors to send letters to Coleman and his Democratic opponent Charles S. Robb demanding they support either the state or the county alignment, which differ for about 10 miles of the 35-mile route. Since Robb had already endorsed the county proposal, Herrity appeared to be placing his own candidate in a bind.

"I don't give a damn whether it helps him or hurts him," Herrity said at the time. "I'm representing the people of Fairfax County here."

Coleman came to Fairfax to urge state-county cooperation on the road, and Herrity said he was satisfied. But not everyone in Richmond appreciated Herrity's efforts.

"This thing has been politicized to an extreme degree," Davis said yesterday. "I think it's unfortunate that anyone would try to use the setting of an election year to try to influence the facts unduly."

"I try to do whatever's best for the people of the county and if that doesn't make other people happy, whether it's the governor, or Mr. Davis, or whoever, that's too bad," Herrity said. "The board and the county had nothing to do with making this a political issue."