Virginia Gov. Charles S. Robb appointed McLean home builder David H. Miller to the influential State Water Control Board last spring, rewarding a loyal supporter who had contributed $1,000 to his 1981 campaign.

At about the same time, the Democratic appointee opened his political checkbook again -- for Northern Virginia Republican Rep. Stanford E. Parris.

Miller is one of many influential Northern Virginia businessmen who helped Robb become Virginia's first Democratic governor since 1969 but who have shunned the congressional campaigns of Democrats Ira M. Lechner and Herbert E. Harris II.

Robb has worked hard to keep the same moderate conservative coalition that helped elect him intact for Lt. Gov. Richard J. Davis, the party's senatorial candidate, but has done considerably less for the two congressional candidates in the Washington suburbs. Some members of the Robb coalition have allied with the Republicans, reflecting their suspicion of Harris and Lechner as liberals in the tradition of populist gubernatorial candidate Henry E. Howell.

"Rightly or wrongly the Democrats nominated someone who is perceived as a liberal Lechner and when that happens a lot of mainstream Virginians sit it out," said T. Eugene Smith, a Robb contributor who was appointed to the state highway commission.

Smith, a wealthy McLean banker, is backing Davis and several Democratic candidates for the state legislature but has stayed away from the area's congressional races.

Lechner and Harris acknowledge they lack the support of some of Robb's financial backers, but said they were not surprised by the individuals -- many of them developers -- who are giving to their opponents. "I don't expect a dime from them and if I got a dime I'd send it back because it would be a conflict of interest," said Lechner, a Washington labor lawyer who frequently represents tenant groups.

"These [builders'] relationships with Stan go clear back to his zoning attorney days," said Harris. Both Democrats say they are pleased with Robb's efforts on their behalf. "I could not ask him to do anything more than he has," Harris said.

Parris' popularity with the Robb conservatives apparently stems from the longstanding personal friendships he cultivated with builders and developers during two decades as an attorney and Fairfax supervisor. Wolf benefits more from antipathy toward former state legislator Lechner and the tenant and union causes he has championed.

"They [the Republicans] are both more conservative in their approach," said condominium developer Giuseppe Cecchi of McLean, a Robb and Davis supporter who has given $1,000 to Parris and $500 to Wolf. "I'm a moderate conservative and Lechner and Harris are extreme liberals."

In addition to Miller and Cecchi, major Robb supporters from Northern Virginia who are helping Wolf or Parris include builder Myron P. Erkiletian, whom Robb appointed to his advisory board on industrial development; engineer Sidney O. Dewberry; land broker Suzanne L. Paciulli, whom Robb appointed to the state Board of Commerce; developers Edward R. Carr and John R. Pflug; and Fairfax automobile dealer Ted Britt.

"That Harris -- he's the wildest liberal that ever lived," said Britt.

Cecchi, a Robb friend and contributor who with his wife has given Davis $2,000, said he previously supported Harris.

"This year, when I'm put to choose between Harris and Stan Parris, I feel Stan is going to be a better congressman, more representative of my interest, which is business," Cecchi said.

Harris and Parris are for the third time fighting to represent the 8th Congressional District, which includes Alexandria and portions of Fairfax, Prince William and Stafford counties.

Wolf, who like Parris was swept into office on Reagan's coattails, is running against Lechner in the 10th District, which includes Arlington, northern Fairfax and Loudoun counties and the cities of Fairfax and Falls Church.

Robb has appeared at countless Davis fund-raisers, stood in for him at debates and stars in two of his political commercials. His Alexandria confidant, lawyer-lobbyist William G. Thomas, said that nearly every builder or banker who supported Robb has hopped on the Davis bandwagon.

It hasn't been a question of Chuck or me twisting arms," said Thomas, who has been a fund-raising leader for the Robb and Davis efforts in Northern Virginia.

"My opinion is they are comfortable with Dick Davis and with his business background," he said.