IF EVER there was in "this gorgeous town" a disarmingly affable broker of political influence who enjoyed the mix of public service, ideas and friendships, it was Thomas G. (Tommy) Corcoran. Mr. Corcoran, who died here Sunday at the age of 80, was a principal strategist, insider and tireless point man for the New Deal revolution during some of its most perilous and interesting times. And "Tommy the Cork," as Franklin D. Roosevelt fondly referred to him, reveled in the role of lawyer-lobbyist (or "entrepreneur," as Mr. Corcoran would put it) in the high circles of all three branches of government.

What Mr. Corcoran knew and marketed so well was "what the government likes and does not like," an insight he mastered firsthand and marketed with great skill. With New Deal architect, White House teammate and longtime friend Benjamin V. Cohen, Mr. Corcoran became an invaluable administration figure and presidential counselor. It was this expertise that he later employed as a lawyer to seek and deliver results on behalf of major corporations that were doing business with the government.

His success in the private sector was a direct sequel to his influential role as engineer-designer of truly revolutionary policies. After all, it was the Corcoran-Cohen duo--known as the "hot-dog boys," an allusion to their mentor, Felix Frankfurter--that collaborated on the big acts, the enduring measures of the New Deal: the Securities and Exchange Commission Act, the Public Utilities Holding Company Act, the Federal Housing Administration Act, the Tennessee Valley Authority and the Wage and Hour Law. In the process, Mr. Corcoran also succeeded in attracting scores of highly capable, dedicated people to government service and important positions from which they were to make substantial contributions to public policy.

If critics had problems with Mr. Corcoran's later transition to private practice in government circles, neither he nor his clients did. Many of the very people who had damned him as a policy-maker were to find him a useful colleague and attorney in those later years, and he found these marriages of mutual interests rewarding in the fullest senses. With his infectious Irish humor and quick repartee, Mr. Corcoran delighted friends, legal adversaries and himself while gliding through the halls and offices of government.

"When I walk down the corridors of the Federal Power Commission," he once explained with a grin to a House subcommittee that was looking into his activities, "it's right down the main aisle . . . in broad daylight, with a brass band behind me." And that is how those who knew Tommy the Cork suspect he has just left their company.