The handsome senator in the black tuxedo had shaken 100 hands. He had smiled 100 smiles. He had made cocktail party small talk with 100 different well-heeled lawyers and the women and men who accompanied them.

But when the stubby man with the curly hair in the brown suit stuck his hand out and said his name was Bill Fenton, a knowing smile flashed across the senator's face.

"Ohhh," he said, looking at a knot of reporters. Don't look over your shoulder, or those guys will be looking for a big wink or something."

Then, Sen. Edward M. Kennedy (D-Mass.), the perennial non-candidate for president, gave that big wink.

It would be easy to say the gesture meant nothing. After all, it was only a gesture, made in jest.

What was fascinating about it was that Kennedy, despite his claims that he is not a candidate for president, knew who Bill Fenton is. Bill Fenton, the Iowa machinist union president, organizer of the first draft-Kennedy group in the nation.

Kennedy had read the newspapers. He had been told who Fenton was. And now despite all the talk about his not wanting to run against President Carter, Kennedy was still playing the game.

The draft-Kennedy people at the cocktail party at the Five Seasons Hotel here had been half afraid to approach Kennedy. What would they do, after all, if he told them all to shut up, to give up all this wild talk about a Kennedy presidency and line up behind Jimmy Carter?

"Hell, I'm not going to shake his hand in a crowded room like this," Art Hedburg, another draft-Kennedy leader, scoffed at one point.

Hedburg was discouraged. Sixteen floors below, the cocktail party demonstrators lined the street, shouting and waving picket signs. The draft-Kennedy people had hoped to attract 200, 300, 400, maybe 1,000 people. They had sent out a memo, to people who had given them money, claiming that they had printed up 20,000 flyers advertising Kennedy's visit.

But now there were fewer than 100 pro-Kennedy demonstrators in front of the big new hotel, and half of them seemed to be more interested in freedom of choice for abortion then Kennedy.

Another 50 across the street were louder. They were anti-abortionists, a big force in Iowa politics, protesting the stands of Kennedy and Sen. John C. Culver (D-Iowa), on the issue.

The street said a lot about the draft-Kennedy movement here and elsewhere.

First, it is not as well-organized as its champions would have people believe.

Secondly, it showed that Kennedy attracts foes almost as easily as he does friends.

Kennedy was in Cedar Rapids to speak to the Iowa Bar Association and to boost the candidacy of his friend and fellow liberal, Culver, who is expected to face a gough reelection battle in 1980.

Kennedy chartered two Lear Jets to bring aides and reporters from Washington here. The speech was an unusual one. A conservative like Ronald Reagan would have felt comfortable giving much of it.

In it, Kennedy railed against big government, red tape and government regulation.

"In many areas of national life, the strength and vitality of America are being hamstrung by excessive laws and regulations," he said. "Businesses flounder in the cost and waste of paperwork. . . . Regulation for the sake of regulation has become an obsessive end of government, instead of a useful means to promote the public good.

"Our lives and our economy are increasingly caught up in an ever-constricting web of laws and regulations that threaten to bring our vaunted free enterprise system to its knees unless we act," he said.

"The traditional American reaction to a problem or abuse has been to say 'there ought to be law,' but now we are to also be prepared to say of many areas, 'there ought not to be a law,'" he said.

Kennedy, chairman of the Senate Judiciary Committee, only criticized in passing President Carter, Against whom he has been pitted in recent weeks.

Kennedy made his trip the same day that three congressmen, who have organized groups to draft him for the presidency, alleged that Kennedy has made no real efforts to discourage their activities.

Hedburg, one of the leaders of the draft-Kennedy group, said Kennedy's office had called him to try to discourage the group from staging a kennedy rally.

"They didn't want Kennedy to overshadow Culver," Hedburg said. "But they didn't tell us not to go ahead. So we did."

Iowa is expected to be a symbolically important state in the 1980 election. In 1976, the state gave Carter, then a relatively obscure former governor from Georgia, his first big push on the way to the White House.

Kennedy's popularity in the state has grown steadily in recent months.

A recent poll by The Des Moines Register found him leading Carter by 40 to 17 percent. That was a 10 percentage-point increase in popularity for Kennedy since a similar poll in February, and a 2 percentage-point drop for Carter.