Sen. Edward M. Kennedy has given hundreds of speeches in a hundred different places since he launched his campaign for the presidency four months ago, but few have been as successful as the Kennedy speech at Mundelein College here last weekend.

The Kennedy who spoke here read a thoughtful, coherent text in coversational tones that gave a ring of real feeling to every sentence. The audience sensed that, and responded warmly; every person jammed into the crowded auditorium seemed to be pulling for the speaker, and by the end of the talk the sense of unity between speaker and audience was almost palpable.

The appearance would have been a coup, in short, for Edward Kennedy or any other candidate. But the speaker and Mundelein was not the candidate -- it was his wife, Joan.

In recent weeks the 43-year-old Mrs. Kennedy has moved slowly and timidly into the fast-moving media-soaked world of her husband's campaign, and in her appearances here and elsewhere she seems to have emerged as one of the struggling candidate's brightest assets.

At the start of Kennedy's campaign it was not clear whether Mrs. Kennedy would emerge at all. She had just finished a successful two-year treatment program for alcoholism, and she refuesed to be pinned down as to how much campaigning she could take.

Today, Joan Kennedy travels with her husband two or three days of most weeks. Occasionally she goes off on her own.

She now grants print and TV interviews most everywhere, and in those sessions, she talks with almost painful openness about the problems that led her to heavy drinking and eventually forced her to leave her family for treatment.

In her personal apppearances, Mrs. Kennedy seems like anything but a polished political performer. But that is what people seem to like best -- the picture of a wife and mother struggling to fit into the world of politics.

Mrs. Kennedy's speeches have the wobbly uncertainty of a baby sparrow's maiden flight, and she seems as surprised as anyone when she succeeds on the stump. At Mundelein, she appeared astonished every time the audience interrupted her with applause -- and it happened 25 times.

Asked two months ago what her interest would be as campaigner or as First Lady, Mrs. Kennedy seemed to have no clear idea. Now, though, she has settled on a topic that evidently means a great deal to her -- the implications of her personal troubles for the women's movement.

"When I first decided . . . to go to Boston for my recovery program," she said here, "it was very hard for me to leave my 12-year-old, Patrick at home.

"I knew the older children would be fine, but Patrick was still my little boy . . . and perhaps the best result of this has been how close my husband Ted has grown to Patrick . . . which brings me back to the central hope: that the end result of the women's movement . . . be a better balance between work and family for everyone -- men and women alike."