Walter F. Mondale gave Edward M. Kennedy a tough act to follow today in his first performance before the Democratic mid-term conference that he and five others hope will be a catapult for their presidential ambitions.

The former vice president, who trails the Massachusetts senator badly in the polls, oratorically won the opening day of the conference with a speech that drew frequent applause and a prolonged standing ovation when he took his final bow.

For a politician often accused of lacking a flair for the dramatic, Mondale gave a speech lambasting the Reagan administration for misdeeds that moved conventioneers as did none of the other aspriring presidential candidates who spoke on the same theme.

Sens. Alan Cranston (Calif.), Ernest F. Hollings (S.C.), Gary Hart (Colo.) and John Glenn (Ohio) were the other speakers. Kennedy opted against speaking as part of that pack today and chose to address the convention Sunday.

For those who spoke, the midterm convention was the place where they hoped to electrify the crowd and earn the right to consideration accorded the established front-runners, Kennedy and Mondale.

That did not happen. Instead, the hall buzzed with mini-attention as they spoke. And in fact, the first notable thing about the Mondale speech was not the noise it sparked, but the silence, actual listening silence.

It was that way in the Iowa delegation that will mean the most, first.

"I have all the respect in the world for him, but I just can't see him being president of the United States," David Manley, a Democratic county chairman from Mason City, said as Mondale walked to the rostrum. He favored Kennedy in 1980 and thinks he will do so again "although I'm taking a strong look at Hart."

But midway through Mondale, Manley whispered: "Boy, he's hot today. He really is hot." When Mondale had finished, Manley was filled with praise and new respect but not quite support.

"That's the best speech I ever heard Fritz give," he said. "That's not the Fritz Mondale I've known . . . . It doesn't quite make me change, but it makes me feel much better about him running."

By the mercurial thermometer with which politicians take each other's measure, an Iowa national committee member, Jean Haugland, said she felt even better than that.

"I'm neutral, although I have a warm spot in my heart for Fritz because we grew up close together," she said before his speech. Afterward, she added: "You remember that warm spot? Well, that speech certainly made it even warmer. Much warmer."

Melvina Scott of Waterloo, Iowa, who divides her time these days between selling insurance and selling Mondale, was bubbling at the end about how much easier it will be to sell Mondale within her delegation. "It was wonderful, spectacular, beautiful--all those words," she said.

How much of Mondale's performance will prove to be negotiable political currency is far from clear because the nominating convention is two years away. But favorable impressions are the principal instruments of this pre-presidential season, and conversions are the coin of the realm.

Today at least, Mondale won a lot of the former and at least a few of the latter.

Before the speech, Caroline Schwarzenwalder, a Washington, D.C., history teacher, said she was uncommitted. Midway through, when Mondale was reciting his litany of what is unfair about "Reagan's America," she told the delegate next to her, "Somebody wrote a great speech." At the end, she pronounced herself leaning to Mondale.

Even close supporters of the other speakers were willing to concede that the reactions to their favorites' performances did not meet their expectations.

As Cranston finished the day's first speech by a presidential hopeful, Nancy Pelosi, the California state party chairman, said she realized that the convention hall chatter had begun to drown out Cranston after the first few minutes.

"Acoustics," she said diplomatically. "It is a real problem here in this hall."

Next to her, California delegate Bert Coffey said: "It's like every other speech--after five minutes, what else is new?"

Mondale, in one politically artful section of his speech, praised specific attributes of his rivals, leaving the clear implication that he alone embodies them all.

"Let the party of John Glenn and Gary Hart give our country a sound strategy for defense . . . . Let the party of Ted Kennedy and Jimmy Carter and Alan Cranston commit this country to negotiating the nuclear freeze . . . ," he said.

Some thought that Mondale today sent a message to the other hopefuls that the 1984 primaries are going to be strictly a two-horse show.

"I think the other guys can forget it," said Philadelphia District Attorney Edward Rendell, a Kennedy supporter. "Mondale was good, and he's got the party machinery with him. Teddy will always have his piece of the party. I don't see where the others fit in."

Hollings, who followed Mondale to the podium, suffered most immediately from Mondale's oratorical triumph. As Hollings started speaking, the crowd that had been so uncharacteristically quiet for so long resumed the familiar hustling and bustling of the convention floor.

Hollings seemed to recapture some attention as he reached the heart of his speech, but his smooth, undulating delivery never equaled, for pure drawing power, Mondale's high-energy, deftly cadenced approach.

Likewise, Glenn and Hart found themselves overshadowed on this particular afternoon.

Hart gave a speech that seemed deliberately to eschew the sort of emotional appeals that work best before a large audience. Theodis Gay, chairman of the District of Columbia delegation, said he thought the content was "excellent, but a lot of its power was lost because of the lack of luster in the delivery."

Glenn, too, had trouble exciting the crowd. "He comes off as pretty much of a loud ho-hum," said Jan Charles Gray, a lawyer and party contributor from Los Angeles.

"To me, he comes off the same way he did in 1976, when Jimmy Carter let him give the keynote at the Democratic convention in New York City to see if he could cut it as a vice presidential candidate . . . . He didn't pass the test then, and I don't think he has come too far since."

On his lapel, Gray was sporting the favorite button of presidential uncommitteds at the conference. It portrays a figure hiding in the bushes and reads: "Wait in the Weeds Gang."

After todays's oratory, Gray was still waiting. He said he found Hart nervous and Hollings unimpressive, and he registered a classicly Californian dissent from the prevailing wisdom that Mondale had stolen the show.

"Mondale I think could have used some Valium," he said.