"I believe in international competition, but I am not a sucker. . . . The key task in the next few years is to stop flying that white flag, to start running up the American flag, to turn around and fight."

That was Walter Mondale haranguing a steel- workers' convention in the heat of last fall's congressional campaign. For his pains, he was quickly labeled a "protectionist" -- a cat's-paw for organized labor.

Tonight Mondale will address the New York Council on Foreign Relations with a speech on "The Power of American Leadership." It will deal more elegantly with the world's economic crisis and our own. And you can bet that this time he will be labeled the new, statesman-like Mondale, as befits his new standing as The Front Runner.

But the new image, to the extent that it conveys trimming and tacking to fit his new condition, will be no more valid than the one he acquired last fall. I say this on the basis of a 21/2-hour conversation with the former vice president, which took place a day or so before Teddy Kennedy's announcement to withdraw from the 1984 race. I came away convinced his prescription for just about everything that ails us defies simplistic or conventional labeling.

His prescription began with an anecdote. At Jimmy Carter's last Cabinet meeting, the president asked those assembled to state what they had learned in office. Mondale recalled Defense Secretary Harold Brown's answer: he had arrived in office with a certain intellectual sense of the interconnection between a strong defense and a strong economy. He was leaving with a powerful, visceral conviction that the connection is fundamental: that you cannot have a strong defense without a strong economy, and that if for no other reason than sound politics, the defense budget has to share whatever constraints are placed on government spending across the board.

Only by putting "our own house in order," Mondale insists, can the United States begin to bring its influence to bear on the global cooperative effort he thinks is urgently needed.

A large part of that effort, he believes, will have to center on measures to promote fair competition between the United States and its trading partners. Some 30 nations have laws requiring a degree of "local content" in what is produced locally; while that's the case, he would apply the same rule to automobiles manufactured in the United States. While foreign competitors subsidize exports with low-interest loans, he would reverse the Reagan policy of cutting back money for the U.S. Export-Import Bank. He would advocate "selective restrictions" on imports that gravely threaten some segments of U.S. industry.

But my sense is that Mondale means it when he insists he is not, in a classic way, advocating "protectionism." Rather, he seems to be thinking in terms of economic "deterrence." He would apply or threaten to apply a variety of import restraints or export incentives for the particular purpose of strengthening the U.S. hand in bargaining for the removal of such inequities in the international trading system.

He is aware that even this tactical resort to "protectionism" can become contagious--and also a comfortable habit of coddling weak industries. He is conscious of the enormous difficulties in defining equity among competing nations with grave economic crises. That he by no means has all the answers is suggested by his decision after 18 months on the political circuit to devote most of the next three months to what he calls "study."