In the basement of the Farmers Savings Bank, a one-story brick building surrounded by the frozen cornfields or rural Iowa, a small drama of democracy took place tonight.

As politics go, it wasn't much of a show -- no bands, no banners, not even a rousing speech. Indeed, to a nationwide television audience watching the Iowa returns, the Beaver precinct caucus was a statistic within a statistic: one of 2,531 neighborhood meetings to elect delegates to a county convention.

But the 109 farmers, factory workers, housewives and students who braved the icy roads to show up and cast their votes helped lay the foundation for the massive, complex process that will end next November in the election of the president of the United States.

For all the passion and hard work that went into the wooing of Beaver precinct's 587 registered Democrats, election of its five delegates -- four for President Carter and one for Sen. Edward M. Kennedy -- was a quiet affair.

The citizens sat in rows of folding chairs. They elected a permanent chairman, Doug Smith, son of the local congressman. They divided into three groups -- 74 Carter supporters on one side of the room, with 10 uncommitted people in a corner, and 25 Kennedy supporters in a separate room. The uncommitted, since they did not constitute a large enough bloc to elect their own delegate, then divided -- seven for Carter, three for Kennedy.

Each group then elected delegates to the March 8 county convention. The county delegates will elect district delegates, who will elect state delegates, who will elect delegates to the Democratic National Convention in New York in August.

The Beaver caucus -- like many, if not most, of these neighborhood meetings-came down largely to a matter of personality. Who works for a presidential candidate, and how hard they work, often has more to do with the outcome than the candidate does.

The referendum at Beaver was as much a vote for Mary Kennedy versus Joe Fitzgerald, as it was for Carter versus Kennedy.

Mary Kennedy, 42, mother of four and a veteran Democratic party worker, arrived at the Farmer's Saving Bank shortly before 8 p.m. with circle under her eyes. In the last new she made some 200 calls, sent 60 letters and held a strategy meeting at her house for Carter supporters. Her aim was to capture all five delegates for the president.

Fitzgerald, 62, a part-time farmer and deputy recorder in the Polk County court house, quietly fumed as he looked around the room for Kennedy supporters.

"When you got a hand-picked few and they run the vote, that ain't right," he said. Fitzgerald jumped into the fray only a week ago, when he learned that the local Kennedy leader had failed to get organized.

The Iowa caucuses are being given such extraordinary national importance that even Beaver precinct got its share of attention. Mary Kennedy's husband, Jim, a store owner in Des Moines, was one of 200 Iowans invited to the White House in October to be briefed by Vice President Mondale and national security affairs adviser Zbigniew Brzezinski.

Yesterday, Joseph P. Kennedy III came to Joe Fitzgerald's two-story, white farmhouse to share coffee and rolls with 33 local residents and answer questions about farm policy and Chappaquiddick.

Fitzgerald, an outgoing man with a shock of white hair and wire-rimmed glasses, said he worked for Carter in 1976, "but he hasn't kept his promises to farmers." Fitzgerald has 240 acres planted in soy beans and corn. With the embargo on grain to the Soviets, he fears he will get far less for his crops than he expected.

Mary Kennedy was a fervent admirer of both John F. Kennedy, whose portrait hangs in her kitchen, and Robert F. Kennedy.

"But we didn't feel Teddy Kennedy is as believable as his brothers," she said. "It goes against my grain to challenge an incumbent."

When the votes were counted, Fitzgerald was bitter.

"Those people for Carter are all the old-time, hard-shell Methodists who won't pave the roads," he said.

Jim Kennedy countered: "A lot of people here would never go into Joe Fitzgerald's camp. He ran for supervisor and lost his own precinct."

In the end, the battle here was won "with hard work -- and what the hell else," Jim Kennedy said.

Fitzgerald, as he walked out into the snowy night, said that sometimes he wondered "if it's worth the neighhood fight."