An old Cuban woman whose monthly rent had tripled to $500, Amelia Rojo, wept as she ambled down Calle Ocho in the heart of Little Havana. She is 75, sunburned and wrinkled, and she lives alone on a $198 Social Security check. She was desperate.

Then she saw the mayor; he would help her. She laughed like a little girl and skipped after Maurice Ferre. She slipped her arm through his and begged him to find her public housing, matching him step-for-step as he stalked votes for a fifth term beneath a hot Florida sun along the same street where crime-plagued Cuban merchants have been realizing American dreams for 20 years.

"I am not a communist," she assured him.

He listened, patted her hand and darted off to court votes over tiny cups of thick cafe Cubano. Amelia Rojo began to cry again.

"There's nothing the mayor can do," said an aide, jotting down her name anyway. "He has no control over Section 8 housing. That's a federal program."

Indeed, Maurice Ferre, like Miami, is suffering from problems not entirely of his own making that he can't seem to fix. And that spells trouble for the Hispanic "honey prince," an upper-class Puerto Rican whose charm and wealth and coalition politics have kept him in office for four terms.

For eight years, he has pushed downtown development and juggled whites, Hispanics and blacks while this tourist boomtown grew into a Hong Kong of the Americas, with an impressive skyline of banks, condominiums and office towers. Then came the riots.

Now, Ferre must grapple with the new political clout of Cubans. The bulk of the city's Hispanics, they make up one-third of the 120,000 registered voters, but represent a voting majority, since they tend to turn out en masse and strut political macho at the polls.

In the past, Ferre enjoyed the Cubans' support as Miami's first Latino mayor. But many Cubans view the Nov. 3 election as their chance to crown Manolo Reboso, former city commissioner and popular Bay of Pigs veteran, as Miami's first Cuban mayor, and also to win as many as four of the five city commission seats.

For many exiles, a Cuban mayor would not only be the highest elected Cuban official in the free world--in effect, a president in exile--but also might signal the start of the same kind of political impact the Italian and Irish immigrants once had.

Cubans are partly inspired by the anti-bilingualism backlash in Dade County, which has a large Cuban population but only one recently appointed Cuban on the county commission. There are no Cubans in the state legislature or congressional delegation.

Now, after 20 years in America, "Cubans have learned a lesson from the system," says Alfredo Duran, ex-chairman of the state Democratic Party and a Reboso supporter who believes Cubans will pick one of their own from the field of seven candidates.

"We realize you have to work hard and make money because the system is based on money, and you have to vote ethnic to maintain political power. Whites voted ethnic white and managed to keep blacks and Hispanics out of power for 200 years. Now it's our turn."

But several polls show one issue cutting across ethnic lines in this bustling seaside city of 400,000: crime. According to 1980 FBI statistics, Miami was the most crime-riddled city in the nation.

Last year, Miami homicides (up 64 percent to 447) crowded the Dade County morgue so badly that the medical examiner had to rent a refrigerated van, the kind used by meat-packers, to house all the dead Juan Does waiting to be identified. In mid-October there were 12 bodies in the deep freeze, 10 of them boatlift refugees whose very presence embarrasses most middle-class Cubans.

One of the victims was delivered from a sidewalk on Miami Beach, where, after the Mariel boatlift, rapes tripled, robberies jumped 87 percent and, according to the Miami News, violent crime as a whole rose 164 percent, all of which led to a tourist season slump of 23 percent.

As the Marielito, an apparent stabbing victim, lay bleeding beneath a yellow plastic sheet, gray-haired ladies on the veranda of the Charles Hotel nearby craned their necks and shuddered.

"He's dead, stretched out, stiff," announced Fanny Gross, a recent immigrant from New York City. "No one's mugged me yet, but we get chains pulled off, and we need police all the time. I always hide my pocketbook with plastic. We make the best of it, but we're scared stiff."

One morgue resident was a mayoral candidate, a bail bondsman who was machine-gunned last spring on the street. That killing led several politicians to start packing guns. Grace Rockafeller, a white-haired civic leader who supports Ferre's chief rival, had to vacate her house after a tear gas bomb sailed through a window this month. She blamed Ferre, who denied any knowledge of the incident.

"It's war," said Bernard Elser, emergency room chief at Jackson Memorial Hospital, where surgeons patched up two gunshot victims one typical afternoon two weeks ago and hospital budget officials struggled over million-dollar deficits from treating indigent refugees, mostly Haitians.

The Coast Guard has tried to help, but the same day it began patrolling off Haiti to stop refugees at the source, a boatload of Haitians landed in Miami. Some natives, outnumbered by the influx of Hispanics and others, are moving to central Florida, or back home. "Anglos in Miami have come to feel like they're living in Russia or Iran," says Rockafeller. "We hide behind double-bolt-locked doors with a gun. And Ferre's attitude is, 'Anyone who doesn't want to speak Spanish can move.' " Some bitterly refer to their city as "the Banana Republic on Biscayne Bay."

"White Anglos want Miami to be like it was," says Ferre. "But those days are gone. How do you explain that to them? "

Marie Petit, the mayor's chief adviser, wonders what people want Ferre to do about Miami's burgeoning drug traffic. "We've got a drug problem, but we don't have an Air Force and we don't have a Coast Guard," she says.

To give Miami a facelift, the chamber of commerce has been flying in planeloads of journalists for expense-paid junkets of sightseeing, speeches and sun. Many go home and write glowing reports that everything is beautiful, no problem.

"When you go home tonight, all the ugliness will be gone because there is darkness," said Manolo Reboso, 46, a Democrat who was Ronald Reagan's co-chairman in Dade County. He was addressing a ballroom crowd of 1,500 supporters at a glittery, $100-a-plate fund-raiser packed with cigar-puffing Cuban power brokers in black tie, among them many ex-Ferre supporters. "But tomorrow the sun will rise and the ugliness will be back. Together, we can make Miami as beautiful in daytime as at night."

The crowd roared its approval of the candidate who has managed to raise $220,000 in a seven-candidate campaign for a job that pays $6,000, outdistancing the mayor in money and some key Hispanic endorsements.

"I will never embarrass you," Reboso promised them, alluding to rumors circulating about an architect-developer who resigned from the city commission to join a real estate firm where he now gets $125,000 a year.

"He's clean as a whistle," said a burly bodyguard who moonlights as security chief at a Miami club that federal agents describe as a favorite haunt of cocaine dealers.

Manolo Reboso makes no effort to hide his close friendship with Anastasio Somoza, the late Nicaraguan dictator who provided a training site for the doomed Bay of Pigs invasion of Cuba. In fact, he revels in it and sticks it to Castro every chance he gets. Miami is perhaps the only city in America where mayoral candidates must have a foreign policy. Anti-communism is a civic issue; Bay of Pigs veterans are heroes.

Reboso is running hard against downtown developers Ferre courted, hitting crime and poor city services. "Miami is not only the crime capital of the United States, but the garbage capital," he says, echoing citizen complaints about crime, soaring property taxes and garbage pickup.

He denies Ferre's charge that he packed friends and relatives onto a government payroll. But he doesn't miss a bite of his thick Cuban sandwich in a Little Havana cafe when asked about another friend, convicted Watergate burglar Bernard Barker, a fellow Cuban who listed Reboso as a reference and found work as a city building inspector.

"He can list me on his resume anytime," said Reboso. "He is my friend and friendship is for life. You are only mayor for two years."

Amigo politics, Miami-style, may catapult Cubans to power, but it threatens to unravel the city's delicate racial and ethnic balance. If Ferre loses to Rebozo and a Cuban wins the only seat now occupied by a black on the five-member commission, a strong possibility according to the polls, Miami's ruling junta will consist of four Cubans, one Anglo.

Such an outcome would further alienate the black community, which represents 29 percent of the registered voters but only had a 16 percent turnout last city election. Many blacks resent Cubans for leapfrogging ahead, Haitians for taking scores of menial jobs.

"Blacks feel frozen out," says Commissioner Theodore Gibson, 65, a black civil rights activist who is stepping down because of arthritis. He says the only hope for blacks and whites to hold on to power is to stick together. "If we can't regroup here in the next three years, this community is going to blow."

To court blacks and Anglos, Reboso has proposed district races that would virtually guarantee each group a seat on the commission.

Ferre has fought back with key black endorsements, and needs the black vote to beat back the Cuban tide. Both candidates have snapped up ads in dozens of Hispanic weekly newspapers, waiting to spend big media money before the wire. Harvey Reisman, a white former city commissioner, is expected to split Anglos with his campaign theme, "Basta Ya!--Enough Is Enough!"

"Little Havana is a garbage dump," says Castro Orestes, 39, a $13-an-hour airline mechanic who voted for Ferre last time. No more. "Three weeks and my garbage hasn't been picked up. My property taxes have doubled. I get no police protection. It stinks."

Many are also irritated by the circus image of the city commission, which took weeks and dozens of ballots to select a city manager, who is black. When the mayor doesn't want the lone black and lone Anglo commissioners to know what he's saying, some critics say, he speaks Spanish. Among their ranks is Armando LaCasa, a city commissioner nicknamed "La Condo" by critics for condominium deals that reportedly helped quadruple his net worth and make him a near-millionaire after less than two years in office. He also lobbied the State Department for a visa on behalf of a Colombian drug kingpin.

"It's just not the year of the incumbent," says Herb Levin, general manager of the largest Spanish-language broadcasting station in Miami. "If you're an incumbent, you're saddled with problems that aren't of your making. Ferre has to answer to crime in the streets, Mariel, drugs. It's more than just ethnic politics. A lot of people just feel it's time for a change."