An emotional mini-drama that took place Sunday night in the Renaissance Room of an unfashionable Holiday Inn here may describe better than anything else how President Carter beat back the "open" convention movement.

The president's forces entered the meeting of the Iowa Carter delegates looking scared.

For days, there had been talk of deep division in the Iowa delegation. Even Carter's state chairman, Clark Rasmussen, had said he might vote with the open-convention group if Secretary of State Edmund S. Muskie became a presidential candidate. More than half the 31 Carter delegates might join him, he speculated.

Iowa has always held a special place in Carter politics. It was there that "Jimmy Who" first attracted national attention with a win in the 1976 Iowa caucuses. And it was there that Carter scored his first big victory of 1980, trouncing Sen. Edward M. Kennedy by 2 to 1.

On Sunday night Carterites rolled out some of their biggest guns. Agriculture Secretary Bob Bergland, whose Norwegian immigrant father once farmed in northern Iowa, was there. So was the president's son Chip, who visited 112 Iowa towns during the last year. So were Tim Kraft, a Carter campaign strategist, Bill Romjue, Carter's Iowa coordinator, and former congressman Michael Blouin, now a Carter appointee.

Bergland and Carter spoke first to thundering applause.Bergland urged everyone to stand firm on "the faithful-delegate issue." Carter said, "I'll do anything in the world you want. Get hot dogs. Whatever. We love you and we need you."

He then shook hands with everyone in the room, calling most people by their first name.

Then came Rasmussen. Kraft, Carter's Iowa field director in 1976, had gotten to him. The chairman, fearing for his political life, was in rapid retreat.

He'd made a mistake, he confessed. He'd been out of touch, bicycling across the state. "I didn't appreciate the implications of the rule," he said sheepishly.

Rasmussen promptly called for a straw vote on the open convention. Twenty-three Carter loyalists said they opposed the rule change, three supported it, and five were undecided.

This was damaging. Kennedy had 17 Iowa delegates. All, along with three uncommitted delegates, were expected to vote for the open-convention rule. The straw vote indicated Carter might not be able to carry the 51-member state delegation on the issue.

But the vote accomplished its strategic purpose. It put every single delegate on the record and in plain view. Carter loyalists then began to lean on the unfaithful. And for the next 90 minutes they leaned hard.

They were both eloquent and brutal.

State Rep. Stephen Rapp warned that the rule could cost Carter the nomination. If the president lost the vote, he predicted that there would be a firestorm in the hall, that it would be very difficult to renominate President Carter.

"I'm asking you to give the president a good convention," pleaded Kraft. "He deserves these four days. We have four days in the sun. Let's not bicker about a rule that's going to be forgotten Tuesday."

Ken Tilp, another Carter partisan, called the open-convention issue a cheap political ploy by cynical Kennedy supporters."Let's keep the table clean," he declared. "We're playing politics and our politics are Carter politics."

Others argued that they would not break faith with the people who elected them, and they thought anyone who did would be guilty of treason.

This was heavy stuff for teachers, factory workers, farmers, and small-time lawyers who make up the bulk of the delegation. The pro-open-convention and undecided delegates spoke only reluctantly and with embarrassment.

Lee Cambell, a schoolteacher from Creston, said he was undecided because everyone from his home area who had contacted him on the issue supported an open convention. "Some of the people who came to me were instrumental in my campaign and are party officials," he said. "I can't turn my back on these people."

Another delegate said he was worried that United Auto Workers union members, who support Kennedy, would desert the party if the vote went against them on the rule fight. At the Iowa Democratic convention, "they said you keep closing the door on us on every issue," he added. "I don't want to lose these people."

When several of the uncommitted delegates and those supporting the open-convention issue turned out to be women, Denis Percel, a Carter alternate, announced he was a white Anglo-Saxon Protestant male, and before the Democrats reformed their rules people like him controlled the party.

"The people who brokered conventions in the past weren't blacks, Hispanics, or women," he said pointedly. "This is a milestone reform. And by damn we can't forget that now."

Miriam Tyson, a black student, retored, "Subconsciously you don't feel confident of President Carter."

When the caucus ended, Carter forces were firmly in control. Democratic state chairman Ed Campbell said, "I think it's all over."

Romjue, Carter's state chairman, had one final request. A phone had been placed on the convention floor between the Virginia and Iowa delegations. "I need some big strong Iowa people to sit beside it," he said. d"It's pretty important to me that the phone doesn't get ripped out."

That, too, was quickly arranged.