This sunbaked city hugs the Mexican border along the Rio Grande River at the bottom of what is known here simply as the Valley, a vast expanse of Texas that sweeps down from San Antonio through hostile ranch land until palm trees dominate the skyline and citrus trees nurture the economy.

At dark, along the highway that runs north out of McAllen, the lights burn brightly at the processing plants, and the fragrance of onions and cantaloupe sweetens the warm tropical air.The odor is powerful in its freshness, seductive as it hangs in the humid night.

Othal Brand came here in 1938 from Georgia, where he remembers proudly the stoop labor he performed in his father's vegetable fields. He came originally as a trucker looking for fruits and vegetables to haul. Twenty-seven years ago, he brought his family to stay, and today he says he is the largest grower in Texas, with acreage across the Southwest and offices of his firm, Griffin and Brand, in London.

And Othal Brand is also mayor of McAllen, a city plagued by its past and uncertain about its future. Its police force is accused of gross brutalities against Mexican Americans, whose growing population and political sophistication suggest that the once-dominant Anglo business community must someday yield its power.

But not yet. Othal Brand is still mayor, reelected in a recent city election that was full of bitterness. He won his second term narrowly, defeating Dr. Ramiro Casso, a physician, with 52.5 percent of the vote. The campaign was as nasty as any anyone can recall, with Brand accusing Casso, a Mexican American, of racism and of fronting for Cesar Chavez and the United Farm Workers Union.

Casso, whose first entry into politics was a successful effort to stop Brand and the city from selling the local hospital to a profit-making hospital corporation, said that Brand's leadership of the city was "immoral" and that the mayor was responsible for making mcallen "a national symbol of police brutality."

Brand ran half-page ads in the local paper with red and black type attempting to link Casso with the farm workers, and shortly before the election he charged large-scale irregularities in voter registration among Mexican Americans -- accusations so far not proved. He used cameras from his company to photograph voters on Election Day. He says he did it to obtain evidence of vote fraud, but Mexican Americans believe he was trying to intimidate uneducated, inexperienced Hispanic voters.

If anything, the election left the city more divided than before, in part because of Brand's defiant personality and because the brutality scandal and Brand's leadership style continue to cause controversy. "His character is so strong that he deals with confrontation all the time," said Richard Salinas, who ran with Casso and won a seat on the city commission.

As a prominent grower, Brand has been the target of efforts by the Texas Farmworkers Union to organize the crews that harvest crops.In 1975, when a group of demonstrators surrounded his car, he emerged and waved a pistol.

"I got out and stopped them with the necessary equipment," Brand said.

He remembers the union organizers pejoratively, as "so-called strikers" with "rifles, sticks, fingernails an inch long . . . who never worked a day in their lives."

Today Brand continues to resist the union with all his power. "I'll not let them take my business and run it," he said.

Brand believes that the problems McAllen is undergoing -- especially the bitter election this spring -- are a continuation of his long war with the union, although others in McAllen believe the city's divisions are more complicated.

One of Brand's main antagonists is a young, dark-haired lawyer named James C. Harrington, who came here from Michigan after meeting and marrying Rebecca Flores at the University of Michigan. His wife, who grew up in Texas, is director of the Texas Farmworkers Union, and he is the union's lawyer. An attorney also for the American Civil Liberties Union, he has been responsible for 26 suits against McAllen or its police department. To date, Harrington said, 25 of those suits have resulted in damages against the city of $410,000.

It was through one of these suits that the existence of video tapes detailing incidents of brutality was made public. Last March, the tapes were introduced as evidence in federal court, and shortly thereafter were broadcast by a local television station. The most shocking showed a young man, Pedro Dennett, being hit repeatedly by several police officers, his head smashed against a table. Over the sound of the punches can be heard his agonizing screams: "Oh, you ass-----. Oh my God . . . I want to make my phone call. I want to make my phone call . . . . Let me go please, please!"

Such beatings were administered in the booking room by officers on the night shift. They called themselves the "C-Shift Animals," had black T-shirts with that name in gold letters, and took a perverse pride in their violent behavior. "You ever been snake bit?" one of the policemen asks a prisoner on one of the tapes. "Well, now you've been C-Shift bit."

They taunted suspects, slapped them, kicked them, punched them, hurled them to the ground. The suspects were almost always Mexican Americans. The policemen who participated in the brutality were both Anglos and Mexican Americans.

Harrington said there are 72 incidents of brutality on tape and reports of another 70 that have been erased. Brand, who first knew of the tapes in 1977, said that of the 72 taped incidents, "only one or two" show excessive force.

"We've cleaned up the police department," Brand said recently, and significant changes have been made. Two police chiefs have been fired in the last few years, 35 to 40 policemen have left the force and, under court order, an intensive training program is being instituted and a human relations commission has been established to hear complaints. Chief Roy Eckhardt said morale is improving, and the recent killing of a young policeman has brought a flood of sympathy calls to a force deluged all spring with outrage over the brutality tapes.

The mayor would like outsiders to believe the city's problems are largely over. But a federal grand jury is conducting a wide-ranging investigation into the brutality and the city's handling of it. Another brutality suit is pending, the bitterness created by attempts to unionize the police force has not been erased, and the divisions from the election remain.

Brand has denied all charges that he either covered up the brutality or moved too slowly in resolving it, and he takes responsibility for bringing in federal investigators. But on May 22, the Texas Senate, on the advice of the local senator, rejected Brand's nomination to a seat on the prisons board after one of the longest hearings on a gubernatorial appointment in Texas history. Brand has filed a $2.5 million libel suit against the Brownsville Herald for its reporting on the police scandal and the mayoral election, saying the paper contributed to his Senate rejection.

In other ways, Brand remains controversial. For example, in appointing members of the human relations board this spring, the city disregarded court requirements that the board represent the economic and racial makeup of the city. McAllen is 71 percent Hispanic and has one of the lowest per capita incomes in the country, but the city attempted to fill its three slots on the five-member board with Anglos. Under threat of contempt of court, the city altered its nominees.

Brand also said the city's rapid growth -- 78 percent in the past decade -- is a root cause of its problems. "I don't think we're the only little country town that outgrew its police department and its services and its leadership," he said.

The Mexican-American community that opposed Brand this spring will not be satisfied until it has ousted the mayor, however. "People think we're dead," said City Commissioner Salinas. "But we're meeting three times a week. We're going to refine what we have. We have a group that is dedicated."