The outcome of the British election and Sen. Alan Cranston's victory in Wisconsin's presidential straw poll have added to organized labor's worries about 1984.
Neither Prime Minister Margaret Thatcher's strong victory in Britain nor the upset of Walter F. Mondale in Wisconsin loom as major blows to labor's hopes for a repudiation of President Reagan at the election polls next year. But the AFL-CIO and its unions may have to reassess their political strategy after setbacks for labor on both sides of the Atlantic.
But Prime Minister Thatcher's overwhelming victory is significant because, to US labor, her conservative policies are distinctly similar to those of President Reagan. Furthermore, economic conditions - particularly unemployment - are comparable in Britain and this country.
The election outcome, in which the Labour Party received the smallest vote in 60 years, is interpreted as a public vote of confidence for Mrs. Thatcher and a vote of no confidence for a government run by the Labour Party. What worries US labor is that the same sort of thing could happpen in this country next year if there is continuing economic progress under President Reagan and the unemployment picture continues to improve.
On the home front, Senator Cranston's win over Mr. Mondale in Wisconsin revives an AFL-CIO policy question: when to endorse a presidential candidate.
Currently, former vice-president Mondale is considered likely to win the endorsement at a federation meeting in December. But Cranston's straw poll victory, although it has no official standing, has boosted the arguments of those who favor delaying an endorsement until after the primaries. They interpret the Cranston victory as a sign that lesser-known candidates in primaries could upset the unions' endorsed candidate and undermine labor's chances for a 1984 victory.
In the past, AFL-CIO unions have split support among candidates in the state primaries. However, this policy has weakened labor's political influence at Democratic conventions later and in presidential elections, according to the AFL-CIO's president, Lane Kirkland.
At the December meeting of its general board of presidents of affiliated unions, the AFL-CIO plans to consider endorsing a presidential candidate. The federation's executive council, which met in May, recommended that member unions ''withhold any final decision'' on endorsements until then, as a step toward solidifying labor support behind one favorite candidate before state primaries get under way.
Mr. Kirkland stressed this in a round of seven regional conferences that wound up recently in Kansas City, Mo. He emphasized the impact that a united labor movement could have to oust the Reagan administration and to ''change the political balance in Washington by breaking the conservative control of the House and containing it in the Senate.''
Conceding that there is ''an element of risk'' in a departure from past AFL-CIO practices, Kirkland says that when the old system fails to work effectively, it is time to try something new.