THE CONTEST for the presidency of the National Organization for Women, decided in New Orleans last weekend, has more significance than most struggles for the leadership of 250,000- member organizations. NOW has helped to establish the tone and set the agenda for the women's movement, which in the past 15 years has changed the substance and style of American life. The contest this time had a certain drama about it: Eleanor Smeal, who was NOW's president from 1977 to 1982, returned from retirement to oppose Judy Goldsmith, whom she had helped to pick as her successor. On Sunday, at NOW's convention in New Orleans, after some 16 hours of ballot casting and counting, Mrs. Smeal prevailed 839 to 703.

"Now," said the victor, "it's time to go back into the streets." Back is the operative word. Under Mrs. Goldsmith, NOW took a leading role in conventional politics, endorsing Walter Mondale's presidential candidacy and later calling on him to select a woman for the vice presidential nomination. Mrs. Smeal is more inclined to, in her words, "raise hell." She wants NOW to sponsor an abortion rights march in Washington next March, and she promises a major effort to revive the now defunct Equal Rights Amendment. She seems undaunted by the fact that in the not-too-distant past similar tactics didn't work.

Like many groups, of the left, right and center, which have been successful in many of their causes but have been frustrated conspicuously in others, NOW must decide whether to seek new causes or to return to failed causes that can still ignite some of the enthusiasm of yore. It has chosen the second course. "You might not get it," Mrs. Smeal says of ERA, "but you get other good things as you go along." She adds, "The ERA has always been our biggest money raiser."

Thus is politics driven by the dynamics of direct- mail fundraising, in which it is usually more profitable to rub raw the sores of discontent than to build a majority coalition. Mrs. Smeal's NOW, like Jesse Helms's Congressional Club, will concentrate on goals that are unachievable in order to rouse the enthusiasm of activists and direct mail contributors. Mrs. Smeal's followers detest Mr. Helms's and vice versa. But neither of their organizations could raise as much money if it could not point to the specter of the other. NOW under Mrs. Smeal will enlist those who want to assuage their frustrations by taking to the streets '60s style. But will it have some more constructive accomplishments as well?