Ernest H. Williams Jr., his gaze as steadfast as the bulldog on the hood of a Mack truck, sat in the rear of the committee room serenely drawing on his pipe.

The legislative committee was debating a tax on diesal fuel, a bill that would hit Williams' clients, Virginia's truckers, hard. But "the judge," as he is known in the halls of the state Capitol, appeared untroubled by the sharp debate before him and didn't budge from his seat during the meeting.

As it turned out, any comments by Williams would have been wasted. The committee voted 17 to 3 to kill the measure.

It was the latest in a long string of seemingly effortless triumphs for the 57-year-old Richmond lawyer who has built an empire and a legend as Virginia's most effective lobbyist while representing one of the state's most powerful special interests. l

"He's one of the best lobbyists down here," says Gov. John N. Dalton, who recently dropped the idea of proposing an increase in truck taxes after Williams persuaded him that Virginia's fees were already among the nation's highest.

"Whatever the truckers pay him, it isn't enough," says Carrington Williams, a former Fairfax County delegate who lost several legislative scraps with Williams over the years.

The judge himself demurs.

"I don't know where anyone gets the idea I'm important because I'm not," says Williams, who refuses to grant interviews because, he says, "publicity doesn't help me one bit."

For all his clout, Williams is an enigma to many here. While other lobbyists are headquartered in the sleek new high-rises that have mushroomed around the Capitol, William operates out of a somewhat shabby ground-floor office in the deteriorating Hotel Jefferson 10 blocks away. He never speaks in committee, never issues a press release.

Because of claustrophobia refuses to ride in the often cramped Capitol elevators and thus seldom ventures to lawmakers' offices. Instead, he plies his trade in the first-floor hallway and behind the closed doors of the exclusive Commonwealth Club, to which he has sponsored many an aspiring lawmaker, including, this year, House Majority Leader Thomas W. Moss.

"The judge is a very charming man who ingratiates himself easily with new members," says Sen. Ray L. Garland (R-Rosnoke), who has clashed with Williams over a number of trucking issues. "He's a master at appealing to people who come here who aren't terribly serious about their work and are looking for social acceptance."

Behind the judge's charm is the enormous powder of Virginia's trucking industry, which influences almost every aspect of the state's economy.

That power was on display two week ago during a Senate finance subcommittee hearing on a Garland-sponsored bill to raise by two-thirds state licensing fees paid by heavy trucks. At a time when the state is desperately searching for more revenue to maintain its roads, the bill would have produced nearly $9 million annually from an industry that a state study says pays less than its fair share of highway costs.

A ragtag coalition of conservationist groups and automobile clubs, who believe the trucks do extensive damage to the roads, along with railroad interests who compete directly with the trucks for freight, spoke in support of the bill.

As is his custom, Williams never said a word, instead relying on Richmond attorney Alexander Wellford, who is kept on retainer by Williams' Virginia Highway Users Association, to present his case at the hearing.

Wellford, who works for one of Richmond's most prestigious law firms, called witnesses from the Virginia Manufacturing Association, the Retail Merchants Association, the Farm Bureau, the Agribusiness Council and the Building Materials Association. Each of them denounced the bill and warned that increased truck fees would increase their business costs and, ultimately, consumer prices.

"If you pass this bill, the price of a quart of milk will go up," warned Phil Cann of the retail merchants.

Heeding Cann's warning, the subcommittee eventually cut out all but one-fourth of the increase Garland has sought. The scaled-down measure passed the full Senate Finance Committee today by 13 to 2, although many observers expect Williams' allies in the House to scuttle it.

"I asked for a feast, they gave me anhors d'oeuvre," complained Garland, who said the reduced bill could be chalked up as yet another triumph for the truckers.

Some legislators say the committee's vote may be an indication that the influence of the truckers and their supporters is fading. As the state has scrambled to come up with new funds for roadways, the old highway lobby that consisted of road builders, motorists clubs, the state highway department and the truckers has begun to fragment.

"They all had common interest for so many years when the money was there, and now that it isn't, they don't," says P. K. Pettus, lobbyist for the Virginia Conservation Council.

Dalton, who received at least $40,000 from trucking interests in campaign contributions when he ran for governor in 1977, has indicated he would sign a statewide gasoline tax increase that included a larger tax on trucks.

Even House Speaker A. L. Philpott, a longtime Williams ally, agrees that because of the highway tax crunch, the legislature must soon study and consider whether truckers are being unfairly subsidized. "We're not out to punish the truckers but we do want everyone to pay their fair share," says Philpott, who notes that his old friend Williams "looks a little more downcast every day."

With the backing of the leadership, the assembly has overwhelmingly approved an investigation of the highway departments's finances by the respected Joint Legislative Audit and Review Commission. The commission's mandate includes an examination of how much each user-group pays for upkeep of state roads.

Pettus says she was happy to see the study resolution passed but notes that a half dozen past studies recommending increases for truckers did little good. "The conclusions have always been the same from those studies and they have always been ignored," she told the House Finance Committee last week.

And other observers say it is much too early to write off the truckers or their chief lobbyist.

"Don't bet against the judge," says a fellow lobbyist. "He's shrewed and he plays this game better than anyone else."