United States trade policies loom as a hot issue in the coming campaigns for the White House and Congress in 1984. Now that organized labor has broken away from its traditional support of free trade and is strongly backing protectionism, front-running Democratic candidates are shifting to the unions' position. At stake for the candidates is labor's support - in money, manpower, and, ultimately, votes.
Those seeking the Democratic nomination aren't alone in a get-tough attitude on imports. Free-trade policies have been under sharp attack in Congress, as a swelling volume of goods from overseas has taken a heavy toll on US jobs and threatens the survival of the country's so-called smokestack industries.
Rep. Bill Frenzel (R) of Minnesota concedes that ''protectionist pressures are waxing hot.''
Rep. Barbara B. Kennelly (D) of Connecticut says free-trade policies are not working, and there is growing public pressure for relief. She says, ''We must do something. Our trade policy must be revamped.''
Most Republicans and some conservative Democrats continue to oppose major reversals of free-trade policies, and the White House appears strongly committed to free trade.
Ardent supporters of free trade question whether President Reagan can stave off changes, if there is no marked improvement in the economy.
A week ago, four leading Democrats seeking labor's support of their presidential bids spoke to a legislative conference of the AFL-CIO's Industrial Union Department. Former Vice-President Walter F. Mondale and Sens. Alan Cranston of California and John Glenn of Ohio supported protectionist policies in bidding for the department's political backing. A fourth candidate, Sen. Gary Hart of Colorado, generally echoed the protectionist position, but he stopped short of full support for labor-sought ''domestic content'' legislation.
Such a bill would require foreign auto and truck manufacturers to use a specified percentage of American-made parts in cars to be sold in this country. Sought initially by the United Automobile Workers, it now has organized labor's full support. Other unions point out that such a law could help electrical and electronic manufacturers and their workers, along with those in a number of other industries.
Mr. Mondale told the labor conference that changes in trade policies are crucial to restoring the US to a competitive footing in international trade.
''I believe in facing realities,'' Mondale said. ''One is that many countries that have free access to the US market close their markets to us.''
Senator Cranston said much the same thing. Senator Glenn, who admitted endorsing domestic-content legislation ''very reluctantly,'' agreed that trade protection for US industry and workers is becoming critical.
Senator Hart, while not giving domestic-content legislation his outright endorsement, promised the union department that he ''would not hesitate to stop cars or other products at our border'' if the countries they come from do not trade fairly with the US.
AFL-CIO has made support for domestic-content legislation and the protectionist concept prerequisites for political endorsement.