President Mikhail Gorba-chev could turn a measured victory into an ulti mate defeat if he misinterprets the outcome of the March 17 referendum on preserving the Soviet Union.

The key challenge to Gorbachev is whether he accepts the plebiscite result as a mandate for change or as a green light for standing still.On the face of it, Gorbachev got what he wanted from the poll: 76.3 percent of eligible voters said they "consider essential the preservation of the Union of Soviet Socialist Republics as a renewed federation of sovereign republics, in which the rights and freedoms of a person of any nationality will be guaranteed in full measure."

The outcome appears to give Gorbachev maximum reward for minimum risk, at least the semblance of a claim to popular support without the danger of exposing himself to direct election.

But a closer look at the result reveals a marred victory that Gorbachev could easily ruin if he does not heed its lessons, starting with the most fundamental one of demographics.

The largest pro-union tally by far came from the five Central Asian republics, where 95 percent of about 30 million voters opposed the country's breakup. Nearly 25 million people, or 70 percent of the voters, supported the union in the vital Ukraine, joined by 5.5 million, or 83 percent, in the fellow Slavic republic of Byelorussia.

Even in the Russian Federation led by Gorba-chev's rival, Boris Yeltsin, 71 percent of the poll participants - something on the order of 50 million people - delivered a pro-union vote.

The returns were strikingly different in the country's largest urban areas.

More people voted against the union than supported it in the three biggest Soviet cities taken as a whole, with the tiny majorities of Moscow and Leningrad offset by an anti-union vote in the Ukrainian capital of Kiev.

Gorbachev's referendum loss in Moscow, Leningrad and Kiev shows how far he has fallen from five years ago, when he was the darling of intellectuals thankful for the freedom of glasnost and excited by the promise of perestroika.

"However important the views of the provinces, big politics is made in big cities," said Vladimir Reznichenko, a commentator for the semiofficial Novosti news agency. "The public there is better informed and politically more active.

"The current government leadership will undoubtedly have to learn a lesson or two from the results of the voting and try, if possible, to promote mutual understanding between itself and residents of the major urban centers, especially the intelligentsia and those known in the West as the middle class," he said.

Gorbachev must also heed the decision in the Russian Federation's separate plebiscite to create a post for a popularly elected president of the republic, which takes up three-quarters of the Soviet Union and is home to half its 290 million people.

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(Additional information)

Just matter of time, Nixon says

Former President Richard Nixon on Sunday visited the Vilnius television center where 14 people were killed by Soviet troops in January and declared that Lithuanian independence was simply a matter of time.

"Lithuania's independence is inevitable," Nixon said, according to a text of his speech released by the Lithuanian government. "It is not a question of whether, but when and how."

Nixon, who is on a two-week tour of the Soviet Union - his seventh trip to the country - said in a speech in Moscow Thursday he had advised his hosts to give the Baltic republics independence and said the issue was poisoning U.S.-Soviet relations.