A New Power in Moscow

BORIS Yeltsin's Russian Republic presidential victory - vanquishing a huge field of candidates and avoiding a runoff - makes him the most powerful politician in the Soviet Union. The West mainly knows Mr. Yeltsin as the sympathetic underdog, a man of the people whose wife, he is fond of saying, stands in line three hours a day like any ordinary Russian wife. Yeltsin has played the populist critic of Mikhail Gorbachev to a T.

Now we will get to know a more complete Yeltsin. As president he plans to institute ``go-fast'' economic reforms and a shift to privatization - a process that proved too frightening to Gorbachev last fall. Yeltsin can no longer play the critic. Does Yeltsin's burly liberal-populist persona hide a demagogue, a minor Mussolini, as some Westerners say? We will find out.

Clearly on the ledger are Yeltsin's actual deeds in recent months. He didn't flinch during Gorbachev's romance with the hard-liners. During the dark winter days of Baltic violence and repression he opened channels to Lithuania. He was able to arrange the nine-plus-one treaty with Gorbachev in April, which led to the election process.

It would be truly sad, however, if Yeltsin continues to play the anti-Gorbachev card as his ace. It is time for Yeltsin to stop defining himself in opposition. To do otherwise will be seen as weakness.

Diplomatically, Yeltsin's victory means the US must open channels to the Russian Republic. President Bush approved $1.5 billion in farm credits to Gorbachev and opened the door to the July G-7 summit in London. US support for the Soviet leader is clear; now it's time to reach out to the republics, something the White House can do when Yeltsin visits this week.

Economically, Yeltsin must mesh the dynamics of his reforms with those of Gorbachev.

Politically, Yeltsin's victory reaffirms liberalization, a good sign. Reform mayors Popov (Moscow) and Sobchak (Leningrad) came in on his coattails.

Socially, Yeltsin can be a moderating influence - among unhappy workers, and even in the military, where he got many votes from the regulars. Economic reform may cause pain. Yeltsin is a leader who may be seen as able to share that pain.