NELSON POYNTER, who died on Thursday at the age of 74, was a marvelous, energetic, responsible journalist who believed, quite simply, that the purpose of journalism is to serve democratic self-government. He found three important ways to put this belief into effect during his lifetime.

Mr. Poynter was best known for having established Congressional Quarterly. Working in Washington during the war, he discovered indignantly - that was how he discovered things - that there was no handy, timely, objective source of information about what a citizen's senator or representative was up to. So he and his first wife, Henrietta, created one, "CQ" - in the first instance a log of roll calls and then a source of information and analysis on all major legislation at each stage in the congressional process.

Few thought there would be a market for such "dry" stuff, but Mr. Poynter had perceived that, with the growth of government, there would be a corresponding growth in demand for information about Congress - and not just about the executive and judicial branches, where most coverage of the period was focused. At one stroke he made it possible for citizens, academics, home-town editors, interest groups, rivals and legislators themselves to keep track of the legislative process. Few innovations have done more to promote accountability in government.

Meanwhile, Mr. Poynter was sharpening the family paper, the morning St. Petersburg Times (which later acquired the afternoon Independent), into an instrument of high professionalism and progressive politics. He made the Times a combative crusader for racial equality, long before Pinellas County started warming to that cause, and it was equally a crusader for honest, enlightened local and state government.

For him there was no contradiction between running a national service and a local newspaper. He believed there really is a federal system, with a national government and strong local decision-making powers, and he sought to provide the information necessary to make the system work at both levels. To the same end, he set up the Poynter Fund, which was his third principal enterprise. Its purpose is to provide special professional training for journalists and to bring journalists into contact with universities and various civic groups.

A good number of us at this newspaper knew Nelson Poynter as a friend as well as a professional colleague and a leader in our business. We respected him for his unique many-layered contribution to both journalism and politics. It is good that the work he did will be sustained in the institutions he created.