MIAMI BEACH, JULY 30 -- The Communications Workers of America (CWA) heard three Democratic presidential contenders today reassert their solidarity with the union movement even though there is little likelihood that labor will endorse a candidate in the 1988 Democratic nomination contest as it did in 1984.

The three -- Massachusetts Gov. Michael S. Dukakis, Jesse L. Jackson and Sen. Paul Simon (Ill.) -- met reporters outside the convention hall after their speeches but refused to take questions from NBC affiliate reporters because the union and NBC are involved in a labor dispute. Today, all news media were locked out of the convention hall by the CWA, after a federal court ruled NBC had to be allowed the same access as other news organizations.

Three others who addressed the CWA on Tuesday before the lockout -- Sens. Joseph R. Biden Jr. (Del.) and Albert Gore Jr. (Tenn.) and Rep. Richard A. Gephardt (Mo.) -- didn't speak until an NBC camera crew was escorted from the hall. Bruce Babbitt, who activated the National Guard during a labor dispute when he was governor of Arizona, did not attend.

Although all the candidates were greeted warmly, CWA leaders and delegates said they saw little chance that labor would endorse a presidential candidate before the primary season begins as it did Democrat Walter F. Mondale four years ago.

"Mondale had earned our support and I think endorsement is a good idea, but 1984 probably wasn't the best time to try it for the first time," said Linda Rasmussen, president of a CWA local in Portland, Ore. "I don't think anybody was going to beat Reagan."

K.W. Flanagan, a delegate from Kansas City, Mo., was even more vehement. "We screwed up in 1984 by selecting so early," he said. "That turned a lot of my people off because it looked to them like the fix was in and they were left out of it. I think a lot of them voted for Reagan as a result."

CWA President Morton Bahr said that there "still is not the level of interest by the membership that I'd like to see" and noted that there was a stronger mood of pragmatism now than four years ago.

"We're looking for whoever is most electable," he said. "It might be a lot like 1976 when the idea was to get as many labor delegates to the {Democratic National} convention as possible. We were all over the lot. All the candidates had some labor support." AFL-CIO rules require a two-thirds majority of member unions to endorse.

The AFL-CIO political works committee will meet in Washington next week to consider alternatives to this rule. Some possibilities include changing the majority to a simple majority, certifying two or three of the candidates as satisfactory or leaving endorsements to local and regional units, Bahr said.

"One change that is healthy is that we are trying to get input from the members, from the bottom up, rather than the top down," he said. "Because all the candidates, Republicans as well as Democrats, were invited -- Labor Secretary Bill Brock urged the Republicans to participate -- to seek the endorsement, we've taken off the curse off what happened to Mondale. No one will be able to accuse someone else of being a 'captive' of labor."

Jackson, an undeclared candidate who told the union members that he had walked many picket lines, including those against NBC, received five standing ovations, the only one to elicit such a reaction.

Simon said he had "identified with working men and women all my life" and said that he told the CWA that what the country needed was presidential leadership that would focus on reducing unemployment.