The AFL-CIO executive council, which will hold its annual gathering this week on the beachfront at Bal Harbor, Fla., is about to turn out for some unfamiliar political calisthenics that could give it either extra muscle or an institutional charley horse.

The exercise, as promoted by AFL-CIO President Lane Kirkland, is aimed at a historical first: to get the labor federation's normally fragmented troops to endorse formally a Democratic presidential candidate later this year, before the first 1984 primaries and caucuses. Conventional wisdom says that former vice president Walter F. Mondale, the front-runner for the nomination, is also the favorite for labor's endorsement.

This ambitious scheme, aimed at maximizing labor's political clout after a decade of dissatisfaction with Democratic presidential candidates, presents problems in addition to the risk of backing a candidate who might ultimately lose. One is the need to keep the process open and democratic while ensuring that the members follow their officers' lead.

The AFL-CIO leaders are sensitive to charges that this plan is a return to the days of political bosses cutting deals in smoke-filled rooms. If they can come up with an endorsement, which requires the approval of unions accounting for two-thirds of the AFL-CIO's 14 million members, they want to be able to say that it truly came from the "working people of America."

They want to be able to deliver the rank-and-file vote, and they want to head off any opposition charges that their candidate has been "captured by Big Labor."

Asked about any stigma attached to a labor endorsement, Kirkland responded with a thin smile: "We will not force it on anyone. Any candidate can reject it . . . . But I'd like to hear him explain to the working people" why they ought not to be among those represented.

But some, including labor insiders, scoff at the idea that the leadership may risk losing control or making a public spectacle of their proceedings.

"Everybody's waiting for this meeting with great trepidation," said one top labor political operative last week. "No one, including myself, can quite believe we can get all these international unions to come to a consensus, to try things out . . . . Everything is up for grabs."

Sen. Alan Cranston (D-Calif.), for one, apparently believes that. The 68-year-old presidential contender has challenged the labor crowd and the press to jog with him and his wife on the beach at 7 a.m. tomorrow. He plans to spend nearly a week at the gathering.

Sen. Ernest F. Hollings (D-S.C.) is the other presidential contender making a formal appearance before the executive council. Aides to other candidates, all of whom have been asked to appear before the council in various forums, are expected.

An appearance by Secretary of State George P. Shultz, the only top Reagan administration official who enjoys warm relations with Kirkland and company, is on the agenda. Labor Secretary Raymond J. Donovan, not invited to address the gathering, has announced he will attend informally.

But possibly more important will be the closed-door meetings of the AFL-CIO's political arm.

When Sen. Edward M. Kennedy (D-Mass.) dropped out of the 1984 Democratic presidential race, the probability that labor could unite for a pre-primary endorsement by year's end increased greatly.

Instead of two old friends of labor pitted against each other, Mondale was left as the front-runner. He, more than any other candidate now, has the two basic attributes that labor leaders say they are looking for: a solid record on labor issues and credibility as a potential winner.

AFL-CIO officials say they are discussing moving their endorsement up to early October if they see a consensus building by then.

Although the endorsement plan requires a two-thirds vote of the federation's members, the actual votes will be cast by each of the 98 AFL-CIO affiliate unions' leaders and other federation officials, about 500 individuals.

A handful of major unions plus some smaller ones, by joining forces, could muster the one-third-plus-one votes needed to deny the endorsement.

There are already rumors of moves by supporters of Cranston and Sen. John Glenn (D-Ohio) to try to win enough votes to block Mondale even if they can't win the endorsement themselves.

Aides to Cranston and Glenn dismiss such tales and stress their candidates' personal clout with labor in their home states.

"If the AFL-CIO endorses Mondale, are they going to work to turn the AFL-CIO in the state of California against Cranston? " asked a Cranston aide. "Are they going to punish labor leaders who work for Glenn in Ohio? "

It is up to each of the affiliate unions to develop its own process for voting on the endorsement question. Many have not yet done so.

Their leaders talk about various combinations of regional conferences, polling, voter education programs and "osmosis" of opinion.

Some will follow the 1 million member American Federation of State, County and Municipal Employes, which plans five regional conferences around the country this spring, where top officials will meet with local leaders to share their readings on the candidates.

But it is expected that in others, the leader will make a command decision.

The building-trades unions are likely to get together and vote as a bloc--their 4.1 million workers make up 30 percent of the federation membership--in order to maximize their influence, according to union sources.

Some may follow the lead of the sheet metal workers, who don't like the process and are balking.