Miami — The leading Democratic presidential candidates dashed through parts of Flordia this week. But like the speedboats that churn through the inland waterways near this charming but politically complex city, the candidates' sounds and effects were only momentary events.
Nineteenth-century railroad builder Henry M. Flagler once predicted Miami would never be more than a ''fishing village,'' though he did build a resort hotel here. But in next Tuesday's primary, Miami and the other crowded cities on this end of the long Florida peninsula will cast enough votes to make their political clout long felt and long remembered.
The votes will reflect the rich diversity of the voters here, a diversity that usually exceeds the ability of any national candidate to capture en masse. Only a few Florida politicians, such as US Rep. Claude Pepper (D), have managed to draw support across cultural and racial lines here.
The voter diversity means that no one group or person can easily dominate others. This results in a kind of obligatory cooperation that has helped the city weather, though not without strain, some tough challenges - including the arrival of more than 100,000 Cuban refugees a few years ago.
''The community is too Balkanized and fractionized to have anyone with political clout,'' says Dan Paul, a Miami attorney active in politics.
The various factions are not easily categorized, according to a number of politically active people here. One of them says Miami is ''liberal,'' while another characterizes it as ''conservative.'' Even among the heavy Democratic majority here, there are, as Representative Pepper said years ago, many Republicans in disguise. They may vote for a Republican presidential candidate, for example.
The complex array of voting patterns and people here includes:
* Many Jewish voters from New York City, who, contrary to the some assumptions, do not tend to be liberal.
* Cuban Americans - among them former Democratic state chairman Alfredo Duran - who do not go along with the more traditional Cuban-American view here that the United States should always take a hard-line approach to Cuba's Fidel Castro. And contrary to some impressions, only about half the Cuban Americans in this area vote Republican, says political scientist Christopher Warren of Florida International University.
* Blacks, such as community worker and political consultant Clyde Pettaway, who backed Walter Mondale instead of Jesse Jackson. And blacks such as Thomas Jones Jr. (see accompanying story, next page) who are breaking out of the routines of ghetto life which were shattered by riots in 1980 and 1982.
''You prevent riots when you begin to create jobs for people,'' says Mr. Pettaway, whose community organization often has had a hard time placing trained blacks in white businesses.
Monsignor Bryan Walsh, an Irish immigrant who heads the area's Community Relations Board, says white businessmen have ''lacked the will to really do something'' about uplifting poor black neighborhoods here. ''The racial isolation of the black community is the underlying disease'' of Miami, he says.
Things are probably improving, he said, ''but not at a pace fast enough to meet the rising expectation.''
Another group of people here in trouble are the Haitians. In legal limbo as their cases are decided by the US Immigration and Naturalization Service, many of them ''are really, really hurting,'' says a lawyer with the Haitian Refugee Center, which itself is running critically low on funds for legal assistance.
But Gary Hart's organizer here, State Rep. Michael Abrams, points to a ''success story'' in the fairly smooth assimilation of more than 100,000 refugees from Cuba in recent years. Though their arrival has ''stretched the social fabric,'' he says, ''I think we've done well.''
Another success story is how the city has become an international banking center for business with Latin America. On the other hand, the war against drug abuse continues, and observers say relations among races and cultures here could be much improved.