Robert E. Lighthizer is no multiple-martini lobbyist. He gave up coffee because of its harmful health effects, then tried tea and decaf, and finally settled on a habitual beverage: cups of steaming hot water.

He quit cigarettes, worked his way through cigars, snuff and chewing tobacco, and now avoids the leaf entirely.

He used to rise at 5:30 a.m. and lift weights or take a run. He still does, but he's added an exercise-bicycle workout in the evening.

The stereotyped image of the back-room, pot-bellied lobbyist faded long ago, and Lighthizer seems to typify the new stereotype that has replaced it. He has all the qualifications: He worked for the committee he now lobbies. He held a high post in the Reagan administration. He has substantive experience in the issues his clients care about.

And like all proper Type A personalities, Lighthizer is successful. In a city where unemployed tax lobbyists are working the phones to find business to replace the bonanza they reaped from last year's tax-revision bill, Lighthizer's biggest problem is excess. His firm has so many clients that he can't accept some applicants -- because their interests would conflict with those of others.

The coming year will feature more of Lighthizer, who has the good fortune to be intimately familiar with Congress' next major legislative priority: trade. Before joining the Washington office of Skadden, Arps, Slate, Meagher & Flom in 1985, he was deputy U.S. trade representative under current Labor Secretary William E. Brock. Before that, he was staff director and chief counsel of the Senate Finance Committee when Robert J. Dole (R-Kan.) was chairman.

Lighthizer, 39, also is closely involved with the organization that will become Dole's presidential campaign if all goes well. He fits the stereotypical image that way, too: If the door revolves back into government, that's just fine.

"He enjoys being part of the exercise of power," said his brother James, county executive of Anne Arundel County. "Like me, that's his passion. This lobbying stuff pays great, but it's secondary. He didn't get involved in government to do lobbying, he got involved in lobbying to get back in government."

The red-haired Lighthizer, who is married and has two children, has a few other passions, among them his red Porsche 911 Targa, his exercise routine and the basketball team of his undergraduate and law school alma mater, Georgetown University. He hired then-Hoya star Patrick Ewing as an intern with the Finance Committee for two summers, and held season tickets even during the period he was working 15-hour days on Capitol Hill.

Particularly in such specialized areas as taxes, energy and trade, the ranks of lobbyists seem to be populated increasingly with former congressional aides. Observers disagree on whether the proportion is rising -- Capitol Hill has always been a breeding ground for the private sector -- but each change of regime seems to send another phalanx of bright young lawyers downtown.

On taxes alone, the rise of Sen. Lloyd Bentsen (D-Tex.) to the helm of the Senate Finance Committee will likely bring new business to former-aides-turned-lobbyists John Raffaelli and Michael Pate. Bentsen's administrative assistant, Charles W. Simpson, is leaving to lobby on numerous issues, including taxes, for the law firm of Lipsen, Hamberger, Whitten & Hamberger.

Roderick A. DeArment at Covington & Burling, who lobbied on the tax bill, came from the Dole staff. William M. Diefenderfer, chief of staff for Sen. Bob Packwood (R-Ore.) when Packwood chaired Finance during the last Congress, joined the firm of Wunder, Thelen & Forgotson late last year. And there are many others.

"Anybody who comes to me and says they want to be a tax lobbyist, I say, go get experience on the Hill. Of course, that doesn't mean you can't get along without it," said Charls E. Walker, a well-known tax lobbyist who has neither a law degree nor Hill experience.

The most important thing that congressional experience teaches, Lighthizer said, is a sense of process and timing.

"The biggest advantage is knowing how the staffs relate to each other, what kind of arguments have tended to be persuasive, so you can decide on what kind of strategy" to pursue, he said. "Having been in those conferences, you have a sense of who has to say what when. You have to go to a member and say, 'Now's the time, if you don't make the point to Mr. {Dan} Rostenkowski {(D-Ill.), chairman of the House Ways and Means Committee} now, it's lost forever,' and realizing how hard the guy has to push, when you should have a paper prepared, when the guy should give the paper, when a constituent should make his phone calls."

In two issues last year, the publication Legal Times dubbed Lighthizer one of the "winner" lobbyists in the tax-revision wars. He worked for a coalition that was partially successful in retaining the deductibility of state and local taxes (the law repealed the deduction for sales taxes). A score sheet compiled by Legal Times also credited him with obtaining a "transition rule" exempting one of his clients from a provision in the law, at a cost to the Treasury of $11 million.

Other issues on which Lighthizer lobbied include an exemption from a provision increasing taxes on companies that merge (a partial victory at best; the exemption may not be legal) and a short-lived proposal to end the deductibility of excise taxes for businesses.

"My feeling is, we did quite well," Lighthizer said. "On some issues, it's hard to tell whether you won or lost -- they were not clear kinds of issues. But our clients' view in almost every case was that we ended up with a product they were pretty pleased with, and certainly one {they} wouldn't have gotten if we had not been involved."

Congressional aides and other lobbyists are somewhat less enthusiastic, pointing out that Lighthizer is a relative newcomer to the lobbying scene and failed to win some transitional exceptions to the merger provisions for some clients, among other less-than-total successes. Even Dole didn't push for everything Lighthizer requested.

But nearly everyone interviewed agreed that Lighthizer will be a hot commodity as Congress writes trade legislation this year. Like taxes, the trade debate offers esoteric provisions granting bottom-line benefits to companies, intense business interest in the final outcome and a host of staff aides who will be assisting in crucial decisions at the last minute, behind closed doors.

Asking senators and their aides for help in such legislative struggles requires a different personality than does carrying out the wishes of your boss -- especially if your boss is the chairman of the powerful Senate Finance Committee. Those who knew Lighthizer in that role say he was a hard-nosed, occasionally partisan Dole operative who negotiated fairly but with little tact.

Will his high-energy approach become the norm for the new generation of lobbyists?

"Some people think 'Light' is abrasive, but I liked him because he would have his facts down to distilled essence. He never used up your time if he didn't have to," said Diefenderfer, Packwood's aide, who knew Lighthizer when both were Senate aides and later when Lighthizer lobbied the tax bill.

The old-line lobbyists "don't need money and so they're not as hungry. It's like boxing, the kid versus the champ. They're a little older, a little slower; they don't want it as much."

BACKGROUND: Lobbyist and partner in the law firm Skadden,Arps, Slate, Meagher & Flom; age 39. Former deputy U.S. trade representative. Chief staff director of the Senate Finance Committee under former chairman Robert J. Dole (R-Kan). BA and law degrees from Georgetown University.