RONALD REAGAN is heading to a summit meeting in Moscow next week which is important for him but critical for Soviet leader Mikhail Gorbachev. If the meeting goes wrong, that is disappointing for President Reagan. It would degrade his place in history, denying him the moderate breakthrough in relations with the Soviets with which he has hoped to crown his presidency.
But for Mr. Gorbachev, the implications of a summit failure are much more far reaching. He is playing a high-stakes game for power and policy change against some entrenched internal opponents.
He needs to prove that he can negotiate successfully with one of the toughest anticommunist leaders in the West - Ronald Reagan. He needs to prove that he can avoid crisis in his foreign relations so that he can concentrate on galvanizing Soviet productivity at home. He needs to guarantee some stability in his relations with the United States, wrapping up a deal on intermediate nuclear arms reductions before confronting the relative unknown in the shape of President George Bush, or the very much greater unknown in the shape of President Michael Dukakis.
Gorbachev has been sending upbeat signals to Washington about the summit. He has proposed a joint Soviet-American unmanned flight to Mars. In an interview with the Washington Post he said the summit heralded ``a turn from confrontation to coexistence.'' He said that ``the winds of the cold war are being replaced by the winds of hope.''
Gorbachev is busy extracting himself from the Soviet Union's most challenging foreign policy problem. With Afghanistan behind him, he would like to calm things down on the foreign policy front to enable him to concentrate on domestic matters and affairs within the communist ``family'' of Eastern Europe.
While the focus of the American and Soviet press will be on the summit in the next few days, swirling around the summit are deep and dramatic political currents in the USSR. They are of major import for Gorbachev and his plans for restructuring the Soviet system within a communist framework.
Looming over the summit is a meeting even more important for Gorbachev, a general conference of the Soviet Communist Party next month. Gorbachev's authority will be on the line there. He will appeal for a mandate for his reform proposals, and that will be a critical test of his strength - perhaps even his future - among the 5,000 conference delegates.
In the run-up to the conference, important shifts in power are taking place. The Communist Party leaders of both Armenia and Azerbaijan have just been ousted. Despite recent ethnic unrest in the two republics, Moscow has apparently been seeking a leadership change for some time. What is not yet clear is which Moscow faction the new leaders in Armenia and Azerbaijan will serve. Some see the changes as intended to install party leaders more congenial to Gorbachev. The changes, however, were presided over on the scene by Yegor Ligachev, who has been cited as a critic of Gorbachev's reform policies, and Alexander Yakovlev, who is a strong proponent. This suggests a continuing uneasy balance in the Soviet leadership between pro- and anti-Gorbachev factions.
Meanwhile, the breezes of change in the USSR are riffling through some of Moscow's client states in Eastern Europe. New leadership has just been installed in Hungary. The new party boss succeeding Janos Kadar is Karoly Grosz, who, although a die-hard communist, wants to galvanize Hungary's economy and has gathered around him some lieutenants with reformist inclinations.
Thus Gorbachev as he heads into the summit balances precariously above swirling currents.