The many portents of Gromyko visit.

This is the week when one man's every move - right down to the shape of his usually ambiguous smile - will be examined for clues. After representing his nation's views to the United States in various capacities for more than 40 years, Soviet Foreign Minister Andrei Gromyko comes to Washington this week for one of his most highly publicized visits ever.

It is obviously not just Mr. Gromyko's week. The week also belongs to Secretary of State George Shultz, who meets the Soviet foreign minister on Wednesday; to Democratic presidential candidate Walter Mondale, who meets him Thursday; and, of course, to President Reagan, who will meet Gromyko next Friday.

But the biggest guessing game for diplomats and the international press will be a matter of reading Mr. Gromyko, not Mr. Reagan or Mr. Mondale. Can the Soviet foreign minister affect the US presidential election in some way as yet unforeseen? Will he agree to continue a dialogue with the United States? As usual, even the obvious questions are not necessarily easy to answer when it comes to the wily Gromyko and his Soviet colleagues. Take this one: Why is he coming to Washington to see President Reagan when, at first glance, it seems to give Reagan a plus for his election campaign?

The conventional wisdom in this city is that any kind of meeting between the American President and a top Soviet, coming as it does after such a long break in contacts at the highest level, will provide Reagan with an election-year advantage. It wasn't long ago that the Soviets called Reagan such a danger to all mankind that they simply could not do business with him. The Gromyko visit sends a different signal.

But the conventionial wisdom - which travels by a kind of instant and easy osmosis among those who call themselves experts here - is sometimes wrong. Gromyko has balanced any impression of favoring Reagan by requesting a meeting with Mondale. And American secretaries of state who have negotiated with Gromyko in recent years have expressed respect for his ability to protect his country's interests in any given situation.

The experienced Gromyko will be meeting his ninth US President when he comes to Washington. He first came to the American capital during World War II and soon became the Soviets' 34-year-old ambassador here. For nearly three decades, he has been foreign minister.

Former Secretary of State Henry A. Kissinger, in his memoirs ''White House Years,'' describes the dour Gromyko as a man who has long been ''the indispensable drive-wheel of Soviet foreign policy, the consummate Soviet diplomat, well briefed, confident, and tenacious.''

But, according to Dr. Kissinger, Gromyko prefers ''steady pressure'' to the bold move. If so, he is probably the right man for this occasion. At a time when the American election campaign is reaching its peak, no one expects breakthroughs, or progress on substantive issues.

It is a time when no American politician wants to be seen to be making concessions to the Soviets under pressure. But President Reagan has a keen interest in showing that he is flexible and that he wants negotiations with Moscow.

Reagan is reported to be planning to propose to Gromyko that the US and Soviet Union undertake more regular contacts at the Cabinet level. Some Reagan administration officials would apparently like to use such contacts to prepare the way for a summit meeting next year between President Reagan and Soviet leader Konstantin Chernenko.

Intensified Cabinet-level contacts could also be used to sound out the Soviets on the possibility of resuming US-Soviet arms control negotiations. American officials are more willing than they were previously to agree to a merging of the talks on intermediate-range nuclear missiles and the now-suspended talks on long-range missiles, should the Soviets want to move in that direction, a State Department official said.

But Gromyko is not expected to promise much in the way of a continuing high-level dialogue with the US. If he went very far in that direction, he might defuse the war-peace issue for Reagan and help hand him the election. But Gromyko is not expected to shut the door to a resumption of such high-level contact. The safe thing for him to do would be to say that the Soviets will study Reagan's proposals.

There are number of reasons why Gromyko might want to meet with Reagan. By refusing to resume arms control talks until the US removes its newly placed intermediate-range missiles from Europe, the Soviets are beginning to look to some Americans, and Europeans, as intransigent. They need to do something to add reasonableness to their image.

As the London magazine, the Economist, described the situation earlier this month, the antinuclear movement in Western Europe has been partly disarmed and Russia had reemerged as ''the world's chief growler.''

Gromyko is widely believed to be at the peak of his influence in the Politburo. His meeting with Reagan could do much to soften that snarling bear image.

US officials say, in the meantime, that Reagan believes he will face Gromyko from a position of renewed US economic, military, and moral strength. While professing a willingness to negotiate with greater flexibility, Reagan apparently does not believe that the US must obtain arms control agreements with the Soviets in order to maintain security.

When two such self-confident men meet, deals can sometimes be made. But until the US presidential election is decided, Reagan may be left with little more than Gromyko's pinched smile.