Lobbyist and former senator Marlow W. Cook (R-Ky.) recalls the telephone call he made on election night in 1980 to Sen. Gaylord Nelson (D-Wis.), who had just suffered a surprise defeat in his bid for a fourth term.

"I told him how badly I felt for him but that he should understand one thing -- that there is life after the Senate," Cook said.

Indeed there is, and for many of the 194 former members of the House and Senate who still reside in the Washington, D.C., area, that life involves lobbying erstwhile colleagues.

Getting a precise count of former members of Congress who are lobbyists is a murky process. By law, lobbyists are to register with the clerk of the House and the secretary of the Senate if they meet all of the following criteria: They receive, collect or solicit contributions to help influence legislation; they make direct contacts with members or their staffs to this end, and their main purpose is to influence legislation.

But many former members who lobby do not consider that they meet all three tests and don't register as lobbyists. Others belong to duly registered firms, but their own names do not turn up on the forms. Enforcement of the registration requirement is through complaints to the Justice Department, but such complaints are very rare. Thus, a count of lobbyists among one-time members could yield a conservative estimate of 50, or a high estimate of 100.

Members who work in some other branch of government after their terms in Congress are among the most high-profile lobbyists. Former senator Richard S. Schweiker (R-Pa.), who served briefly as secretary of health and human services, is now president of the American Council of Life Insurance, and former senator Edmund S. Muskie (D-Maine), who was one of two secretaries of state in the Carter administration, handles international and environmental clients for a law firm registered to lobby.

Former members obviously enjoy some advantage in having entree to their former colleagues. They have access to the floors of the House or Senate and to the members' gyms and dining rooms. But most don't make too much of it.

"I've never been on the floor since I left unless the Senate was out of session and I was showing a guest around," said Cook, who served one term, from 1968 to 1974, and is now a partner in a law firm that has banks, insurance companies and oil and gas industry firms as lobbying clients. "I go to the gym occasionally but I've never been to a Tuesday policy luncheon, which I regard as a courtesy extended to me if I'm not involved in anything -- which I am."

The greatest advantages accrue to former members who held powerful positions on committees with financial and tax-writing clout. Former representative Wilbur D. Mills (D-Ark.), for years the chairman of the House Ways and Means Committee, is now a lobbyist for the law firm of Shea & Gould, which is registered to lobby for Mars Inc., Nabisco Inc. and the Hospital Corp. of America, among others.

For all the advantages, many former members don't make it as lobbyists after the first year or so.

"Some just don't land lucky and are on the fringes for a year or two and then they disappear from view," said former representative James G. O'Hara (D-Mich.), an 18-year veteran of the House who lost a bid for the Senate in 1976 and now lobbies and practices law with the firm of Patton, Boggs & Blow. "They were helpful to an interest when they were members and got a contract for a year or two and then it ran out."

Cook and O'Hara are examples of former members who have succeeded spectacularly well in their lives after Congress, and who evince a minimum of regret at being on the other side of the fence. For starters, they now are paid several times the current annual congressional salary of $75,100.

"I was always a rules and procedure maven," O'Hara said. "I spend about three-fourths of my time on legislative work and the rest lawyering."

Passage of the Chrysler bail-out bill is one instance of his knowledge of House procedure. O'Hara helped Reps. John E. Brademas of Indiana, then the Democratic whip, and James A. Blanchard, the floor manager of the bill and now governor of Michigan, to work out the legislative strategy. Opponents, O'Hara said, "were caught asleep at the switch."

Lobbyists usually don't work on issues of that magnitude, however.

"Generally, we're working on details of both major and minor issues like looking for a vehicle to attach something to," O'Hara said. He cited "a provision that continued the FCC's power to regulate the cost of attaching cable TV wires to telephone poles instead of letting the telephone company do it. I think we attached it to a Goldwater bill on ham radios or something like that, but the problem these days is that so little legislation is moving."

There is also less interaction with the White House than in the past, because "this administration doesn't get involved except at veto time," O'Hara said.

The biggest changes in lobbying, however, are due to changes in the Congress. The revolt against the leadership in the 1970s stripped the major committee chairmen of much of their power and made it necessary to contact members on an individual basis.

And the workload, according to Cook, has increased accordingly. Members of Congress, he said, are "so busy it's difficult to get hold of them." Serving in Congress "doesn't seem as much fun as it used to be."

"We've got a white jacket in the closet here, one that wraps all the way around to the back for anyone who interviews with us who expresses an interest in returning to elective politics," he said.