Sen. Edward M. Kennedy (D-Mass.) has moved far enough into the 1980 presidential race to choke off any momentum in the labor-for-Carter drive -- but not enough to create a draft-Kennedy stampede by union leaders.

The officers of six major unions who endorsed President Carter last July are still with him, contrary to earlier predictions from the Carter camp, their ranks have not swelled and now show no signs of doing so for the foreseeable future, union sources say.

Even some of the six feel a pro-Kennedy "tide rising under them" from their members, according to one nominally pro-Carter union leader. Defection from the group are considered possible, although probably not likely soon.

At the same time, only one major union president -- William W. Winpisinger of the International Association of Machinists -- has publicly committed himself to Kennedy and he did so before the senator acknowledged earlier this month he may challenge Carter.

Winpisinger, who has launched a dump-Carter, draft-Kennedy campaign, is a maverick on the AFL-CIO Executive Countil and not altogether popular with his more conservative colleagues. "The ones who don't like him, what do they do? He's co-opted the field," said one pro-Kennedy unionist.

There is also caution, born of some earlier political battle scars, about moving out early with an uncertain candidate. Many cite American Federation of State, County and Municipal Employes Union President Jerry Wurf's early embrace of Sen. Edmund S. Muskie (D-Maine) in 1972. Wurf is now urging exploration of alternatives to Carter but remains assiduously uncommitted.

"Why should we be asked to stick out our necks when the senator (Kennedy) won't do the same?" asked one unionist.Said another: "Until Kennedy really moves, there's simply no pressure."

Even more important, some say, is a reluctance to slap a sitting president, considering the enormous leverage the White House has over economic, trade and other issues of bread-and-butter importance to labor unions.

Incumbency puts a brake on pro-Kennedy sentiment in many of the biggest unions.

The United Auto Workers desperately wants federal aid for faltering Chrylser Corp. The garment unions owe a debt for trade concessions; the National Education Association is linked to the administration in their joint push for a separate Department of Education. The Brotherhood of Railway and Airline Clerks, which has a vice president (but not its president) on the Carter labor committee, has a lot at stake in Amtrak legislation and other rail matters.

Rank-and-file pressure for Kennedy is reported in most of the unions with officers participating in the Labor for Carter/Mondale Committee. The six unions are the Communications Workers, Retail Food and Commercial Workers, International Ladies Garment Workers, Amalgamated Clothing and Textile Workers, Seafarers International and Brotherhood of Railway and Airline Clerks.

Local officers of some, including the big communications and garment unions, serve on state and local draft-Kennedy campaigns.

Murray H. Finley, president of the Amalgamated Clothing and Textile Workers Union and a member of the Carter committee, and there is "no question" that Kennedy has strong support in his and other unions.

"What happens if Kennedy makes it official . . . we'll see later," said Finley when asked recently if he would reconsider if Kennedy declares his candidacy. He noted that he was speaking for himself rather than the union in endorsing Carter.

An aide to Sol Chaikin, president of the International Ladies Garment Workers Union, said Chaikin had made it clear from the start that he would have to "take another look" if Kennedy runs.

Winspsinger's group is talking about recruiting some union presidents to sign a letter aimed at soliciting a massive draft-Kennedy response from the labor movement, timed to coincide with the opening of the biennial AFL-CIO convention here in mid-November.

But Carter loyalists interpret Winpisinger's failure to recruit any of his colleagues so far as a sign that "we've turned the corner" with respect to labor support for Kennedy, as one of them put it. He said the labor-for-Carter group is making "steady progress," pointing to the recent appointment of a staff for the committee.