Florida's November Republican presidential preference convention, created last May to spotlight the state nationally as the earliest prize in the crowded party race, has turned into a unmanageable monster that nearly everyone involved now wishes would go away.

They have concluded, however, that it won't. And some candidates' campaigns are spending hundreds of thousands of dollars as the pre-convention caucuses begin this week on what many of them, as well as state party officials, now see as a meaningless exercise.

The Florida GOP convention is a strange hybrid: a cross between the Iowa-style party caucus and the traditional beauty contest. Designed by a Miami advertising man to attract media attention to conservative candidates before next winter's contests in Iowa and New Hampshire, the Florida convention is only advisory, with no direct impact on the selection of delegates to the 1980 GOP convention.

In the meantime, state party officials say, energy spent on the convention is damaging their fund-raising for the critical March primary.

Here's how the convention works. From Aug. 18 through mid-September, each county will hold a GOP caucus. Any registered Republican in that county may show up to apply to be a delegate to the Nov. 17 convention in Orlando.

Twenty percent of each county's delegates will be picked by a specially appointed committee. The rest will be chosen by the luck of the draw: Their names will be pulled from a hat.

In Orlando the approximately 1,450 delegates will gather to express a first and second choice for the GOP presidential nomination.

But party officials and candidates' supporters say that vote will be inherently unrepresentative, and, at best, a test of a candidate's ability to generate a mob scene. Because probability is the way to play the game, the presidential campaigns will be trying to turn out four or five hopefuls for every single delegate slot. The result, some fear, will be riotous scenes as thousands cram into small restaurants and halls in what may be the largest series of political meetings in the history of most counties.

"We expect 10,000 people trying to be delegates," even if each presidential candidate has only one person applying for each slot, said Bill Taylor, Florida GOP chairman. "It may go as high as 20,000," he said. Some candidates' aides doubt this, specualting that Republicans instead will be over-whelmed - and apathetic.

Beyond the confusion, Republicans foresee other potential problems:

- Because the Federal Election Commission places limits on total spending in each state, all the campaign directors here - especially those for former California governor Ronald Reagan and former Texas governor John Connally, who are expected to spend the most money - are desperately worried that they are cutting into Florida's spending limit by as much as one-third and will not be able to spend sufficiently for the primary.

- Some also worry about what to do with all the partisans the convention activity stirs up during the seven months between the county caucuses and the primary. "We're going to turn on a lot of people," said Harry Davant, Connally's Florida manager, "and we're not structured to handle them and we won't be for months."

- Party officials, who dreamed up the idea as a way of drawing media attention to their state, now say it has severely cut into their own fund-raising drives. In addition, it is beginning to cause factional strife in some counties that the Republicans, a distinct minority party here, can ill afford.

Many candidates' campaigns and party officials are treating the convention with dismayed resignation.

"I've never seen anything like this in all my years in politics," said Pat Hillings, a former California congressman running Reagan's campaign in Florida. "You can turn out 10 times as many people as anyone else and still not win."

"It's absurd," said Don Sundquist, Sen. Howard H. Baker Jr.'s national campaign director.

Many observers believe that news reporters, bored by waiting for real action in the presidential race, will focus attention on the Florida convention, and that a candidate could be embarrassed by a poor showing.

"You'd like to say this is just crazy and ignore it," said David Keene, of the George Bush campaign. "But nobody will."

There was an effort to do just that - ignore it. Davant said Connally aides approached other camps to see if some mutual agreement could be worked out - but unsuccessfully "Nobody liked the idea [of the convention]," he said. "But each one thought his man was being sandbagged."

So, with the direct-mail campaigns, telephone banks, caucus-day car brigades and other activities generally reserved for the real thing, the campaign is on full strength.

The Democratic Party has a similar convention, for which partisans of Sen. Edward M. Kennedy (D-Mass.) are vigorously preparing an effort to embarrass President Carter. But the Democratic Party process is more representative because delegates to the state convention will be elected in party caucuses rather than selected at random.

"What really terrifies me,", said GOP chairman Taylor, "is what's going to be said and written about us on March 11, when the primary election comes and produces a totally different result from the convention. I don't see how this can help but happen."