The 500 barons of organized labor who gather next Saturday to bestow one of the first big prizes in the 1984 presidential campaign want to show that they act not as kingmakers in a smoke-filled room but as champions of the 14.5 million bricklayers, bartenders, government clerks, airline pilots, seafarers, teachers, hospital orderlies, bottle blowers and other workers whose votes they will cast.

The fundamental question of how well the labor leaders reflect the concerns of their rank-and-file has already struck hot intramural sparks.

The labor endorsement is one-third of a potential weekend triple play for former vice president Walter F. Mondale that supporters are hoping will rocket him to a solid autumn lead. The National Education Association's endorsement will be announced Friday and the crucial Maine straw poll takes place on Saturday.

Anticipating that the AFL-CIO and its 96 affiliated unions will endorse Mondale, campaign strategists for Sen. John Glenn (D-Ohio), his chief rival, have intensified a tricky effort to challenge the integrity of the process and to peel off as much rank-and-file support as possible.

But the federation leaders saw them coming.

According to a newly released AFL-CIO report, its unions reached out and touched their members in a variety of ways this summer:

* The Clothing and Textile Workers distributed opinion surveys in English and Spanish to all U.S. locals. More than 25,000 reportedly were returned, computerized and analyzed by an independent professional.

* The Communications Workers conducted several polls, including one computerized random mail sample of 10,000 members.

* The Service Employes conducted several polls, including a telephone survey by an outside firm, and mailed preference ballots to 64,000 members registered as Democrats and another 20,000 union activists.

* The Bakery, Confectionery and Tobacco Workers mailed 1,560 confidential presidential preference ballots to local officers and other activists.

* The Steelworkers distributed a 17-question survey to the top officers of every local in the United States.

* Other unions held consensus-building meetings, passed resolutions or collected reports from local leaders.

Union officials' lips are sealed about the specific results of this pulse-taking until the general board convenes at 9:30 a.m. Saturday in a Hollywood, Fla., meeting room--open to the press--to reach its final decision.

But a sampling of major unions indicates that nothing has shaken the overwhelming consensus favoring Mondale.

Leaning heavily on recent nationwide polls, Glenn's operatives suggest that if Mondale gets the two-thirds majority--9.75 million votes--required to win the support of labor's beefed-up political machinery, something fishy is going on.

"Glenn shows good strength in union households," said his campaign manager, Bill White. "And in no poll does Mondale run well enough to suggest he has the support of two-thirds of union households in the country."

As for suggestions that the general board demonstrate its solidarity by giving Mondale a landslide, White said, "If Mondale comes out with 90 percent, it won't pass the smell test."

At the same time, Glenn aides say they are walking a tightrope to avoid running an anti-union campaign. They are using a technique that has proved successful in most of Glenn's Senate campaigns, where except in 1980 he lacked the support of Ohio union leaders but appealed directly to the rank-and-file.

In addition to ducking the top leaders and making his pitch to regional and local union activists, Glenn also is sending letters to all union presidents urging them to split their votes Saturday, giving him his fair share of all those union polls and straw votes. On Friday, Glenn was making the rounds in Beaumont, Tex., trying to show grassroots union support.

Some unions reportedly are still making up their minds how to play it, weighing their desire to show a unified labor movement against their desire to appease internal political pressures.

Others are resisting Glenn's importunings.

Marty Hughes, a Cleveland labor official who belongs to the Communications Workers of America, is widely recognized as Glenn's point man within organized labor. But his own union is planning to throw all its half-million votes behind one candidate, according to CWA political director Loretta Bowen. Hughes, as a local AFL-CIO official, may cast one vote for Glenn.

And the membership of the Paper Workers Union, in which President Wayne E. Glenn supports candidate Glenn, reportedly gave Mondale a narrow majority win in its own membership poll.

The Florida general board meeting will allow for two hours of open discussion on the endorsement.

If no candidate gets two-thirds on the first ballot, a second roll call will include only the top two.

If this fails to produce a two-thirds majority, the AFL-CIO will make no pre-primary endorsement.

"With the intensity of the Glenn activity, I wouldn't rule out the possibility of a second ballot," said Mondale aide Paul Jensen, adhering to the policy of insisting that their candidate has no lock on the endorsement.

Some Mondale backers and labor insiders say Glenn is playing a dangerous game that might cost him some labor support if he does ultimately beat Mondale out of the nomination.

Some observers also say his campaign was slow to realize what an impact the labor endorsement would have.

"He's way behind the curve, trying to catch up and doing it badly," said Mondale aide Bob Beckel.

"This process has been wide open from the beginning and the Glenn people didn't take full advantage of it," said AFL-CIO spokesman Murray Seeger. He cited "a lack of sophistication" in their organization.

Glenn aides were surprised and awed at an AFL-CIO executive council meeting in Boston last month, according to several of them, when labor officials described the scope and sophistication of the grassroots political operation they have developed. The aides emerged with an estimate that the endorsement would be worth $20 million to the chosen candidate.

But when the council voted to advance the endorsement date from December to Oct. 1, a signal that labor support was running for Mondale, Glenn was forced to accelerate his belated effort.

"We always knew it was important," said one Glenn operative, "but I don't think we ever anticipated" how much it would be worth.

Of Glenn's argument that labor support should reflect national polls, Seeger said this: "I suspect that there were more union people surveyed in our union polls than in any polls Glenn has....Organized labor has never done anything like this before."