Wein the chattering class have made a great deal of the weak hand Mikhail Gorbachev will be playing at the Washington summit with President Bush. But what of Bush's clout at this historic juncture? Will he loom like the Colossus of Camp David, raw power rippling through every gesture as he claims victory in the Cold War over the supine Soviets?

Gorbachev has little to fear on this score. Looming large is not in Bush's nature or the nature of Potus, as the president of the United States is known in government cables. The KGB will certainly have shown Gorbachev a May 21 news dispatch out of Portland, Ore., that speaks volumes about the state of Potus at the ember end of the 20th century:

''About 150 to 200 people demonstrated outside the hotel where Bush spoke, burning American flags and newspapers and setting off smoke bombs. The demonstrators were demanding that the president list the spotted owl as an endangered species.''

It is the dignity and authority of Potus that sounds endangered when his fellow citizens treat his office with such frivolity. I can't pretend to have absorbed the merits of Oregon's spotted-owl crisis, but the burning of flags in its name outside George Bush's hotel window pings in my ears as the kind of false note that is increasingly mistaken for political discourse in America.

Gorbachev at least is wrestling with important demons. He confronts daily tests of national survival and definition. He is not matched against fools who imagine that burning a flag is a political statement about spotted owls. Nor does he suffer that other set of fools who conspire to turn flag burning into political action by passing catch-all laws against it.

Yes, Gorbachev arrives in Washington harried, beleaguered and profoundly unpopular at home. But he arrives in fighting trim, with his natural toughness sharply honed by the demands his citizens make on him. Politically, Gorbachev goes 10 rounds every day against Muhammad Ali in top form and somehow gets through it. Bush's opposition is so mediocre that he barely works up a lather jumping rope. Except, of course, for that scuffle last December when Bush knocked out a drunken former sparring partner named Noriega.

The Soviet leader brings a seriousness of purpose to this summit that will serve him well. Gorbachev knows now that he is not engaged in a fancy diplomatic negotiation about the ''architecture'' of Europe. The Soviets are engaged in the most difficult and dangerous military maneuver of all: a strategic retreat of a vast, overextended occupation force.

Like Napoleon pulling back from Moscow, the Soviets must extricate 400,000 men from the deepening quagmire of East Germany, which will cease to exist within a year as it is absorbed into West Germany and NATO. This is the most urgent and most concentrated topic Gorbachev and Bush will discuss.

At a minimum, Gorbachev will want U.S. blessing or acquiescence for an increasingly intimate Soviet-West German economic relationship that will pay the costs of the Soviet withdrawal and help stabilize the Soviet economy.

West German construction firms could soon be building barracks inside the Soviet Union to house returning troops if Moscow formally requests such help. The Soviets say their housing crisis at home is the greatest physical obstacle to withdrawal and therefore to a smooth unification process.

The principle the Soviets want to establish is that they will not be made to suffer militarily or economically as they surrender the gains of the only clear accomplishment of Soviet power since the 1917 revolution: the victory of the Red Army over Hitler's forces on the Eastern Front.

A Soviet general made that point by probing insistently in a recent conversation with West German officials to see if Soviet soldiers would be able to convert large holdings of East German marks at the favorable rate Bonn gives East German citizens. The officials surmise that the general and his mark-heavy comrades accumulated their holdings through illegal trade and equipment sales. ''It is loot,'' says one Bonn insider. But the West Germans seem ready to offer the enterprising Soviet generals payment in hard currency to go quietly.

Soviet troops will also need financial aid from Bonn to help with local costs during the transition period between unification and final withdrawal. ''They are going to be a poor army in a rich country. They won't be able to buy anything with rubles,'' said one West German official.

The bad choices he has made on the economy and Lithuania and the consequences of German unification appear to overwhelm Gorbachev at the moment. But the Germans and Russians are about serious business. They are forging new nations and new destinies out of the collapse of the postwar order. Whatever the result of the summit and whatever Gorbachev's fate, they are condemned to continue this process.

History makes leaders as surely as leaders make history. The demands the people and conditions of the Soviet Union place on Gorbachev are probably beyond any mortal's capability. They do weaken the hand he holds at the summit.

But unlike Potus, Gorbachev will never risk being accused of having underbid his hand.