The AFL-CIO has revised its campaign strategy of support for Walter Mondale by joining him in a strident attack on Gary Hart, his strongest rival for the Democratic presidential nomination.
It is another big gamble for the AFL-CIO and its president, Lane Kirkland. It could - and did this week in New York - strengthen the former vice-president's labor vote by condemning Senator Hart as a candidate ''yielding to the program of Ronald Reagan.'' But if Mr. Mondale should lose the nomination to Hart in July, the AFL-CIO would face a difficult time establishing political credibility in backing the Democratic nominee.
This concerns many in the AFL-CIO ranks. There are reservations about moving further out on a political limb by antagonizing the man who still could turn out to be the Democratic candidate in November.
In October 1983 the federation endorsed Mondale, the first time it had committed its support to a candidate before the Democratic primaries and caucuses. At the time, it planned to work for its candidate without criticizing his opponents. The AFL-CIO leadership was confident Mondale would be an early and strong front-runner and winner.
But Hart upset AFL-CIO plans. He quickly became a viable candidate, receiving strong support from union members in several states, most recently from the recorded 51 percent of them in Connecticut. After his New England sweep, Jan Peerce of the Communications Workers of America campaign staff said labor had overestimated Mondale's appeal to unionists, who seemed to be ''more attuned to listening to television promises than to their union leaders.''
Along the way Mondale won in Michigan, Alabama, Illinois - states with large union blocs that supported him. But labor's successes were mixed, so the AFL-CIO has revised its strategy.
The AFL-CIO now will attack Hart in direct campaign appeals to union members, warning them, in Mr. Kirkland's words, that the Democrats ''cannot beat Reagan with just a little bit of Reaganism. We don't need a choice in November between two Liberaces at the same piano. For working people that's a sure loser.''
In New York, where labor was already for Mondale, the intensified AFL-CIO campaigning was a factor in his estimated 2-to-1 margin over Hart. But the real test will come in Pennsylvania next Tuesday and in later campaigns, where the AFL-CIO is confident it can cut deeply into Hart's union support.
Now the AFL-CIO is making it clear that it is not only for Mondale, but also against Hart. It says the former vice-president's opponent is appealing to ''anti-labor independents and crossover Republicans,'' using ''a little bit of watered-down conservatism, laced with a slug of old-fashioned isolationism.''
''We are not buying that. We'll take our liberalism straight,'' Kirkland told Pennsylvania unionists in urging all-out support for Mondale in next week's primary.
While conceding that Hart, a candidate labor endorsed and supported in the past, voted in the Senate with the union position more often than not, the AFL-CIO says his ''wrong'' votes have come on some of labor's high-priority proposals.
According to the AFL-CIO, Hart has ''broken with the Democratic mainstream as well as the labor movement'' over important issues.
Moreover, it says, although Hart accepted labor support - and money - in the past, and ''sought and failed to win support'' in his present campaign for the Democratic presidential nomination, he has ''reacted with spite and malice'' to labor's endorsement of Mondale. The AFL-CIO says he has sought to portray the former vice-president as ''a captive of unions.''
Kirkland is leading the attacks on Hart, warning trade unionists that Hart's new ideas for the presidency offer little to labor.
In raising arguments against Hart, Kirkland said he is merely clarifying differences between the candidate and labor - pointing out issues on which Hart's ''record falls short.''
These issues include unemployment benefits, the minimum wage for teen-agers, job safety, housing policies, hospital costs, aid to improve education, and budget priorities.
Labor leaders also fault Hart for voting to weaken legislation with ''buy American'' requirements for steel, concrete, and other construction material purchased with federal funds and for opposing labor-sought legislation that would require imported cars to include US-made parts.
''He's against legislation to keep jobs here in the United States; so is Ronald Reagan,'' Kirkland told Pennsylvania unionists, who will be voting in their state's primary on April 10.
''He claims to love working people, but he insults their organizations; so does Ronald Reagan. He wants to restructure social security; so does Ronald Reagan. . . . He told Chrysler workers to drop dead (a reference to Hart's opposition to a financial bailout of Chrysler), so if anybody else gets in trouble, they'd better not count on him.''