Dan Rostenkowski was born the year that Al Smith, the first Catholic nominated to be president, was overwhelmed in the 1928 election by the Protestant Republican, Herbert Hoover.

He grew up thinking that he and other Catholics could never by president, and when he went to the 1956 Democratic convention and saw John F. Kennedy denied the vice presidential nomination, that bitter truth of American politics seemed confirmed.

Four years later, Rostenkowski was a freshman congressman, "working like a son of a buck to elect Jack Kennedy president." He recalls the excitement when Kennedy visited his overwhelmingly Catholic district on Chicago's northwest side, how the people turned out hours ahead of time to catch a glimpse of the young man from Boston.

It was not just that the Democratic nominee was visiting a Democratic city, Rostenkowski says, but that Kennedy was "young, Catholic, had been discriminated against," and it made a huge difference.

"That brought us all together," he said. "Goddam it we had people coming out to vote we thought were dead."

It is now 1980. Over the years, Rostenkowski has risen to a position of influence in the House and in the political power structure of his home city. Last fall, he went before his fellow Cook County Democrats and argued vehemently that they should not jump on Edward M. Kennedy's bandwagon, but should follow their tradition of running uncommitted delegate slates in the March 18 Illinois presidential primary.

Rostenkowski lost the argument, and so went about the business of visiting his district, which is still heavily Polish and Catholic, where the people live in neat rows of brick bungalows on narrow lots.

"I was amazed," he said, "at the number of people who came up and whispered, 'You're absolutely right, he shouldn't be president.'"

Twenty years after John F. Kennedy broke the presidential barrier for American Catholics, his brother, Sen. Edward M. Kennedy (D-Mass.), is in as much trouble in this heavily Catholic city and its suburbs as he appears to be nationally.

The reasons for this are as diverse and complex as the ethnic backgrounds of this city's people. Kennedy is suffering here as much as anywhere from the stumbling beginning of his national campaign. The senator's image as a big-spending liberal is not all that appealing to white ethnic Catholics, many of whom equate government programs with welfare, and welfare with blacks.

And all the publicity about his personal life, even the stories about the secret lifestyle of the martyred Jack, have tarnished the family image to the point that some say a southern Baptist president is viewed as "a better Catholic" than Kennedy.

Rostenkowski is not the only political figure here to be surprised that the third Kennedy brother to run for president seems not to have touched the hearts of the Irish, Polish, Italian and other Catholics who make up an estimated 45 percent of the city's population and about half of its Cook County suburbanites.

"five months ago, the prevailing wisdom in Washington was that there would be a massive move by white ethnic Catholics here to Kennedy, and an equally massive move by blacks," said Larry Hansen, President Carter's Illinois campaign coordinator. "Neither has happened."

For the Kennedy campaign, this is a gloomy prospect. The senator is now concentrating on his home region of New England, fighting to keep his candidacy alive there, and forced largely to ignore Illinois until after the Feb. 26 New Hampshire primary.

Last fall, Illinois looked the place where the Kennedy bandwagon would go into high gear. Even if Carter retained an appeal in the small towns and farms downstate, it was assumed that Kennedy would run strong in the Catholic, traditionally Democratic areas of Cook County. If the Kennedy "magic," the Kennedy mystique, didn't take hold here, it was hard to see where it would make a difference.

But now, Cook County looks like the place that could break Kennedy's campaign, if not his heart.

One reason for Kennedy's problems here has nothing to do with national political issues but with the fact that Kennedy's most prominent Catholic supporter, Mayor Jane Byrne, is the wild card in the Cook County political deck.

Byrne's change of mind last fall, turning in a matter of days from a near-endorsement of the president to an all-out embrace of Kennedy, has not gone over well with many of the Catholics of Chicago, who have been schooled by both the church and the local Democratic organization to play by the rules.

"There are ways to do things," said Jim Sherman. Sherman runs the district office here for Rep. Martin A. Russo (D-Ill.), a self-described "moderate Democrat" who is supporting Carter.

Russo's district is miles south of Rostenkowski's, and 70 percent of it is in the suburbs. But the two areas are not that much different. When the Irish and Polish Catholics of southwest Chicago fled the city in the face of black migration into their neighborhoods, they moved to suburbs such as Oak Lawn and Alsip.

Sherman estimates that the district is up to 70 percent Catholic. A poll of its suburban areas last fall, just before the Iranian crisis, showed Carter leading Kennedy among Democrats by about 2 to 1.

"It's ironic, isn't?" Sherman said, pointing to the three pictures on the wall of his office on South Cicero Avenue in Oak Lawn. One picture is of Russo, and another of Russo and the president. The third picture is of John F. Kennedy.

"There's not a strong identification of Ted Kennedy as a Catholic, even among traditionalist Cahtolics," Sherman said. "He's seen as a guy who has taken positions opposed by the bishops, who is separated from his wife . . . he's seen as a guy who is trying to usurp something that's not really his, riding his brother's coattails."

There is wide agreement here that being Catholic will not help Kennedy much, even in an area where Catholic Democrats have dominated politics for generations. Among some segments of the Catholic population, for most of whom the quesiton of abortion is the overriding issue, there may be a backlash.

Among others, Kennedy's Catholicism, his cultural ties to the descendants of Irish immigrants, may linger strong enough in the emotions to be a mild asset. But like the other Catholic Democrat running for president, California Gov. Edmund G. (Jerry) Brown Jr., he cannot count on a solid "Catholic vote." His brother took care of that 20 years ago.

John Kennedy got 78 percent of the Catholic vote in his victory over Richard M. Nixon, but only 38 percent of the Protestant vote, according to a Gallup poll at the time. A new Washington Post poll shows that Edward Kennedy is drawing some extra support among Catholics, but far less than his brother did in 1960.

Kennedy is currently behind Carter by 51 to 33 percent among Democratic Catholics interviewed by The Post, but behind by a much sharper 63 to 23 percent among non-Catholics.

"Catholics are much more cosmopolitan than they were in 1960," said Father Dennis Sanders, 39, the principal of Weber High School, a Catholic instituion for boys in the heart of Rostenkowski's district. "We are an accepted people. Once you're accepted, you don't have to fight for it."

"I wish," the priest added, "that I could be for Kennedy because of my kind."

In 1960, John F. Kennedy was not anxious to confront directly the so-called "religious issue." It was an ugly undercurrent in presidential politics then, and the original Kennedy campaign strategy was to put it off as long as possible.

"But decisions in a campaign are forced on one by timing of emotions over which no one has control," wrote author Theordoe H. White of John Kennedy's decision to appear before a panel of Protestant ministers in Houston on Sept. 12, 1960 to swear unending devotion to the principle of absolute separation of church and state.

Edward M. Kennedy appeared to have made a similar decision of timing this week, when he appeared in television commercials shown in New England, and for the first time brought up the subject of the Chappaquiddick incident himself, asking voters to believe his version of what happened.

Like religion in 1960, Chappaquiddick will not go away. People as diverse as Andrew Greeley, the South Side Irish priest who is associated with the National Opinions Research Center at the University of Chicago, and a young Polish alderman from the northwest side of Chicago, asked what troubles people in their areas had about Kennedy, replied that Chappaquiddick is high on the list.

"Most people are not as charitable as his wife," Greeley said. "They don't believe him. That's an enormous problem."

The alderman adds that "Chappaquiddick is probably his biggest problem," particularly among the more traditionalist, generally older Catholics of his ward.

"Last summer, if you asked me, I'd be singing a different tune," he said. "Before he was a candidate, he was a very popular person. People didn't think about Chappaquiddick and so he was floating along. Then he became a candidate and people started thinking about it."

But Kennedy's problems over the more than a decade-old incident are not confined to traditionalist Catholics. Rostenkowski knows a young woman in his district, a lifelong Democrat with a looser lifestyle than many Catholics of earlier generations would have found acceptable.

She has confided to the congressman that she could never vote for Kennedy. "He could have saved that girl," she said.

State Sen. Jeremiah Joyce, graduate of St. Sabina elementary school, Leo Catholic High School and DePaul University law school, is supporting Carter for president.

Joyce lives now west and south of where he grew up, in the part of Russo's congressional district that is in the city. Many of his boyhood friends moved in the same direction with him, and so the area remains overwhelmingly Democratic and Irish Catholic.

Last fall, Joyce was under conflicting political pressures as the presidential race approached. The county organization, headed by Bryne, was rumored leaning toward Kennedy.Russo was clearly going to back Carter, and that was also Joyce's inclination.

But he was also worried, remembering 1960, when he was not yet old enough to vote but could see how "everyone was out ringing doorbells for John Kennedy." He wondered how the sons and daughters of the generations that took so much pride in John Kennedy's election felt about Ted Kennedy.

So he took a poll. It was nothing fancy or even scientific, at first just conversations with friends, who were asked to ask other friends, and finally random telephone calls to people selected not by their precinct but by their parish. It was the week before the Iran crises broke.

"It was 4 or 5 to 1 against Kennedy," Joyce said. "I was overwhelmed by the numbers. I don't see where he's going to get any support if he can't run well here."

Gerard Doherty, the Kennedy campaign coordinator in Illinois still has hope. The 1980 presidential race has already been extraordinarily volatile, and anything can happen between now and the primary. There is a good deal of talk about Carter's call for draft registration and that could hurt the president.

There is also no way to know what the final emotions of Kennedy's fellow Catholics will be. "When they go into the ballot box and see the Kennedy name there, there'll be a tug," Greeley said. "How strong a tug will depend on the events of the next few weeks."

Joyce, however, does not see much room for sentiment. With that sense of inevitable finality the Irish are known for, he said:

"Yeah, my wife and I, Tom Hynes [the Cook County assessor] and his wife and some of us talked about it.

"Did you even believe we'd be coming out against a Kennedy?' we said. I'm sure my grandfather would be turning over in his grave. But I'm not unique. All my contemporaries out here are Irish Catholics and I suppose their grandfathers are turning in their graves, too. So be it."