France's Le Monde reported from Venice that there was one point not in doubt at the summit meeting of the world's seven leading industrial democracies: ''that Ronald Reagan was determined to sign an accord with the Soviet Union as soon as possible on the removal of nuclear missiles.''

Although the allied leaders at the conference are apparently convinced of this, Reagan continues to encounter difficulty in persuading citizens of Western European nations that he is indeed committed to reaching an agreement with Mikhail Gorbachev.

Last week, as Reagan tried once more to reassure West German pacifists that his heart is with them -- that he, too, seeks a world free from the threat of nuclear annihilation -- reports leaked of a new poll of Europeans showing Gorbachev the clear winner in the 1987 ''peace war.''

The poll, sponsored by the U.S. Information Agency, showed large margins of British, French and West Germans give Gorbachev more credit than Ronald Reagan for progress toward an arms agreement. In Britain, 63 percent thought Gorbachev deserved the credit as compared with 13 percent who gave the credit to Reagan. In West Germany, it was 72 percent for Gorbachev to 9 percent for Reagan. In France, the Soviet leader was credited over the American leader by 45 percent to 16 percent.

Our European friends do not even give Reagan credit for initiating the proposals he did, in fact, initiate. For example, large majorities think Gorbachev first proposed the ''zero option'' for removal of intermediate-range nuclear missiles from Europe.

Europe's leaders know better. They understand that Ronald Reagan is, as one said, ''hellbent'' on signing an agreement with Gorbachev.

What accounts for the great gap in perception between allied leaders and the European public? For one thing, leaders are better informed, often at firsthand.

The people are more susceptible to propaganda and stereotypes. Publics respond to deep-set impressions. As Walter Lippmann explained in his brilliant book, ''Public Opinion,'' publics understand public figures through oversimplified stereotypes that resist change. Information that contradicts these stereotypes tends to be ignored, forgotten or reinterpreted.

For much of the world, European as well as American, Ronald Reagan is seen as a John Wayne figure -- a tall, strong, laconic defender of freedom.

During his first term, he played the part and won widespread kudos for a polished performance -- with his speech to the British Parliament, his visit to the beach at Normandy. By promoting a strong dollar and a strong America, offering solidarity to the people of Poland, supporting the mujaheddin in Afghanistan, the contras in Nicaragua, insisting on the reversibility of tyranny and the inevitability of freedom, Reagan made his mark. With the Reagan Doctrine, he projected a vision of the future that contradicted Marxist claims and affirmed that freedom works better than collectivism or force. Reagan seemed almost typecast for the role he played. No wonder he did it so well.

The president's new message does not fit the old role or the old Reagan. It involves too much contradiction with too many past positions. Reagan saw too many flaws in past arms control agreements and spoke too often about how and why they left the United States and its allies weaker and the Soviet Union stronger. He spoke too often about the Soviets' expansionist tendencies and the necessity for strength. The old message not only criticized specific arms agreements, it criticized the ''arms control'' approach to American and Western security.

The president and his advisers claim there is no contradiction between the old message and the new posture. But Western publics think otherwise. Some are dismayed by Reagan's new enthusiasm for sweeping arms agreements. Others are disbelieving. Almost no one is ready to applaud Ronald Reagan for signing an agreement that counters his teachings of a lifetime.

There is a moral in the Western publics' reluctance to credit Ronald Reagan with a major role in arms negotiations. It is that Ronald Reagan cannot establish his place in history by signing an arms accord -- no matter how dramatic.