Howard and Frances Jones, formerly of Middlesex, N.J., came across the Florida border on I-95 with all their earthly belongings piled in the back seat of their Chrysler.

Jones, 61, had retired nine days earlier. "We sold everything and just left -- the house, all the furniture, everything we had collected over the years," he said. "We don't know where we're going to live or what we're going to do. We came to that time in life where we just decided to move on."

Florida is full of people like the Joneses, 20th century pioneers who have uprooted themselves, headed for the sunshine and in the process changed the character of the Sunshine State.

"Florida is basically a Styrofoam, paper-plate society," said Craig Farmer, a former executive director of the state Democratic Party. "People don't have any roots. They are moving in and out all the time."

In 1984, 367,000 people -- 1,003 a day or 42 an hour -- moved into the state; another 45.7 million -- or 87 every minute -- visited as tourists; six of the 11 fastest-growing U.S. cities were in Florida. By 1990, the state is expected to become the nation's fourth largest -- behind only California, New York and Texas, up from 20th largest in 1950.

But it isn't just size that gives Florida an increasingly significant political role and makes the 1986 Senate race, expected to pit incumbent Republican Paula Hawkins against Gov. Robert Graham (D), intriguing.

This land of exiles and rootlessness is a place of experimentation and vast internal conflict, a trend setter, for good or ill. Florida not only has the nation's highest growth rate, it also has the highest rates of deaths, divorces and crime, according to a recent University of Florida study.

James Naisbitt, who has made a national reputation spotting trends, argues that Florida "may soon surpass California" as a bellwether state.

"By carefully watching what is happening now in Florida, we stand to learn a wealth of information about the problems and opportunities the whole nation will face in the future," he wrote in his bestseller "Megatrends."

"The reason is demographics," Naisbitt said. "In 1980 Florida had the nation's oldest population and Floridians experienced growing tension between the state's older and younger residents. This conflict is especially noteworthy, because by about the year 1995 the entire U.S. population will reflect the same age-youth ratio that Florida has now." Test-Marketing the Issues

As such, Florida's 1986 Senate race promises to become one of the nation's premier political testing grounds, a place to test-market political issues, from Social Security to Central America, and experiment with political techniques, from direct mail to negative advertising.

Others doubt that Florida has become a bellwether. They view Florida as a political enigma with a peculiar identity. But, because of its size, dynamic growth and population mix, few dismiss its importance.

It is difficult for many to think of Florida as a trend setter. Few states have a more firmly established image in the American psyche: Florida, the fantasy land, the haven for the Social Security set, a place of oranges and alligators, Disney World and Cape Canaveral.

The pop-culture themes most often associated with the state are sun, sex, gangsterism and the search for eternal youth. They have been celebrated in movies like "Where the Boys Are," about the sexual escapades of vacationing college students at Fort Lauderdale, and "Cocoon," a current film about retirees seeking lost youth; the television series "Miami Vice," which focuses on drug busts in Florida's largest city; and the mystery novels of John D. MacDonald, whose best-known character, Travis McGee, lives on a houseboat and drives a Rolls Royce chopped into a pickup.

Vast (by road, Pensacola is closer to Chicago than to Key West), poor and sparsely populated, today's mega-state was a backwater much of its history, part of the South but not of the South.

St. Augustine was already a thriving 55-year-old community with a seminary and a hospital by the time the Pilgrims landed at Plymouth Rock, but for centuries the state was largely uninhabited swamp. As late as 1898, Miami was a sleepy fishing village of 300 residents.

When naturalist John James Audubon visited in 1832, he described Florida as "a garden, where all that is not mud, mud, mud is sand, sand, sand, where the fruit is so sour that it is not eatable, and where in place of singing birds and golden fishes, you have a species of ibis that you cannot get when you have shot it, and alligators, snakes and scorpions." Sand, Sun and Real Estate

Other states were settled by people seeking religious freedom, land or gold and shaped by statesmen, generals and industrial giants.

Florida, named Pascua florida or flowery Easter by the Spanish explorer Ponce de Leone, was settled by people seeking sun and sand and shaped by real estate promoters. After the beach, phosphate, a major component of fertilizer, is its only natural resource.

Two of the most important figures in Florida history were two such promoters, Henry M. Flagler and Henry B. Plant. Plant opened up the citrus growing regions of the state with a railroad connecting the Atlantic port of Jacksonville with the Gulf Coast port of Tampa, where he built the exotic Tampa Bay Hotel.

Flagler opened up development of the state's Atlantic coast with a railroad built to serve a series of Flagler luxury hotels for the wealthy -- the Ponce de Leon in St. Augustine, the Breakers and the Royal Poinciana in Palm Beach and the Royal Palm in Miami. Flagler's Florida East Coast Line eventually reached Key West.

The Plant and Flagler railroads gave Florida its first statewide communications system; made the state, which has 1,000 miles of coastline, accessible to tourists for the first time; and set the stage for the first great Florida population boom after World War I.

But in 1940 Florida's population of 1.8 million was still smaller than that of any other southern state. Fuel for the Boom

What changed that?

Air conditioning, which made the humid climate livable; the jetliner, which made a once-isolated peninsula accessible; Social Security and retirement pensions; and Fidel Castro, according to Gov. Graham.

Wave after wave of migrants arrived in the state after World War II.

Jews came from New York; factory workers from Michigan (the United Auto Workers once boasted that Florida had more UAW pensioners than palm trees); small-businessmen from Ohio; retired farmers from Iowa and Illinois; and political refugees from Castro's Cuba, then from Haiti, Nicaragua and other Latin American countries.

Northeasterners generally settled on the Atlantic coast of South Florida; midwesterners on the Gulf Coast and in Central Florida. Hispanics made Miami a major center of Latin American commerce. Only the piney woods of North Florida and the Panhandle retain any semblance of the Old South.

The new Floridians retained emotional attachments elsewhere. "I live in Florida and consider myself a Floridian," said Jeb Bush, son of Vice President Bush and chairman of the Dade County (Miami) Republican Party. "But I grew up in Texas and a part of me will always be a Texan."

Conflict was inevitable.

Blacks resented the rapid economic gains made by Hispanics, who now make up 45 percent of the population of Dade County.

The needs of retirees conflicted with those of young parents.

The economic interests of powerful developers conflicted with the environmental concerns of newcomers who came to enjoy the state's beaches and waterways.

Florida today is a place in flux.

Its natural beauty has been soiled by runaway growth (the state has 30,173 billboards and 374,254 mobile homes); its people are divided along racial, ethnic, geographic and generational lines; and its fragile environment is strained by overdevelopment and an unending series of natural disasters -- runaway fires, freezes and hurricanes.

The state's economy is shifting. Florida is being transformed from a state emphasizing agriculture, retirement and tourism into one focusing on business. Disney World attendance dropped 7 percent last year.

Since 1979, 706 firms with about 128,000 employes have moved here, according to the state Commerce Department. Jobs in existing industry have mushroomed. Banking, high-tech manufacturing, defense and trade-related industries led the way.

At Martin Marietta Aerospace, Orlando's largest industrial firm, employment has nearly doubled in the last five years, to 11,000 workers.

The population explosion has moved. Central and southwestern Florida are the state's fastest-growing regions; its fastest-growing cities are Naples, Ocala, Fort Pierce, Fort Myers and West Palm Beach.

Senior citizens still lead the migration, and 18 percent of Floridians are over age 65, compared with 11 percent nationally. But the newcomers are more affluent, better educated and more conservative than in years past. The leading cargo shipment out of Tampa International Airport is tropical fish; human remains are second.

Florida politics are disjointed, volatile and personality-oriented. "This is the natural habitat of frontier land," said Miami Mayor Maurice Ferre. "This is no different than the Wild West 100 years ago."

"It's a TV state," said Charles Black, Hawkins' top political adviser. "Eighty percent of the voters weren't born in Florida; another 30 percent have moved in the last 10 years. So there isn't any political culture, ties, tradition or understanding of state politics. Instead of listening to local opinion leaders, people rely on television."

The state has eight major "media markets," but no single dominant city, television station or newspaper. Instead, it has many centers, each with its own problems and promises: Miami, the largest; Orlando, home of Disney World; Jacksonville, the old Gateway City; and Tampa-St. Petersburg, the Gulf Coast giants.

Democrats have dominated state and local offices here since Reconstruction, but the state has voted Republican in every presidential election but two (1964 and 1976) since 1948, and GOP registration is on the rise, especially among Hispanics.

Almost 10,000 of them registered Republican after a naturalization ceremony held in the Orange Bowl last year. Republicans Ascendant

"There's no doubt Florida isn't as Democratic as it once was," said Bill Hamilton, a Democratic pollster working for Graham. "The older people who are moving in are more affluent and more Republican than they once were. There are more Cubans and fewer blacks. You also have a lot of retired military people, some high-tech types and young people who have the same conservative attitudes as young people in the rest of the country."

University of Florida political scientists David Colburn and Richard Scher contend that Sunshine State politics are "generally nonideological and even relatively issue-free. In many gubernatorial contests, it has been hard to tell which candidate has been the more liberal or conservative. Often they have said much the same thing, and voters have had to tell them apart on the basis of their tone, style, personality and county of origin."

"Basically people in Florida have been a forerunner in voting for the person, instead of the party," said Steve Ross, a longtime Democratic power broker in Miami. "We've always been southern and western here.

"When I first came to Florida I learned that what political historian V.O. Key said was true: 'In Florida, it's every man for himself.' It is still every man for himself here. You really need something to separate you from the pack. Some call it a gimmick. I call it an attention-grabber."