MOSCOW -- Boris N. Yeltsin will face the most difficult test of his leadership since the days of the August putsch when a session of Russia's most powerful legislative body opens here tomorrow.
Having yanked Russia onto a course of painful and abrupt economic reform through a series of unilateral presidential decrees, Mr. Yeltsin has stirred up his resentful opponents within the parliament to a near-fever pitch.
Now, they see their chance to strike back through the latest session of the Congress of People's Deputies, a broad-based, constitution-making body that only meets every six months or so.
The Congress will be asked to approve a new constitution and to debate Mr. Yeltsin's economic reform program.
Mr. Yeltsin is both president and prime minister of Russia. His opponents are demanding that he resign as prime minister, along with his Cabinet, so that the brakes can be put on the country's plunge toward an unbridled free market.
They also hope to strip from him the power to rule by decree.
One deputy, Yuri Slobodkin, proposed eliminating the presidency altogether and replacing it with a collective leadership.
Viktor Aksyuchits of the Russian Christian Democratic Movement said that a coalition of parties called the Russian Popular Assembly wants to create a new Cabinet to replace the government of "national humiliation and poverty," and if thwarted will set up a "shadow Cabinet."
This Cabinet, said Ilya Konstantinov, another deputy, would be composed of leaders distinguished by "competence and patriotism."
Mikhail Bocharov, once head of the Soviet Union's Supreme Economic Council, accused Mr. Yeltsin's government of "fleecing the people" by setting prices free.
After a torpid winter that saw none of the civil unrest predicted by alarmists, despite food shortages and soaring prices, Moscow seems alive again with politics.
Every imaginable faction is out demonstrating. Communists, Christians, trade unionists, populists, and anarchists are emerging as if from hibernation. Newspapers are urging the government to follow the Polish model, the Chinese model, the Hungarian model, the Yugoslav model (seriously) of economic reform.
Yet Mr. Yeltsin holds some very strong cards. For one thing, no single politician commands the respect of all the opposition forces, making it difficult to see who could replace him.
Second, two of the most visible critics of his economic program -- the chairman of the parliament, Ruslan Khasbulatov, and Vice President Aleksandr Rutskoi -- both said last week that they will support the government.
Mr. Khasbulatov even pointed out, rather mildly, that no one could accuse Mr. Yeltsin of abusing his emergency powers.
The Yeltsin government has also eased up a little on its economic program.
It delayed setting the price of oil free until later this spring and said this week that it would begin to make credits available to industries converting from defense production. That step will make a balanced budget impossible and risk setting off a bout of steep inflation, but it should cut down on plant closings and unemployment.
Mr. Yeltsin himself shuffled some of his key players last week. Most importantly, he replaced Yegor Gaidar, the architect of his economic policy, as finance minister, although he left Mr. Gaidar in overall charge of economic reform.
Gennady Burbulis, another top economic expert and a man the opposition loves to hate, resigned Friday as vice premier but will stay on as state secretary.
Mr. Yeltsin made it clear he didn't intend to bend further. He said he is against "throwing the brave, united, young, reformist Russian government to the dogs."
Moreover, the Western industrial nations announced a $24 billion financial aid package last week, widely seen here as a very influential vote of confidence in Mr. Yeltsin's government.
The issue of a new Russian constitution also promises to be a muddled one rather than a straightforward one, which will probably be in Mr. Yeltsin's favor. For months, a special constitutional commission has been working on a new national charter, which is to be submitted to the Congress.
But even though Mr. Yeltsin was a member of that commission, he has been backing away from its proposal.
Now, Anatoly Sobchak, the reform mayor of St. Petersburg, has submitted a different constitution, one placing a heavier emphasis on the protection of individual liberties.
This led not one but three parties on the Communist side of the spectrum to draft their own proposals, so that there are now five different constitutions on the table and only a day and a half of the nine-day session of the Congress in which to consider them.
The greatest likelihood, then, is that none will be approved. Mr. Yeltsin has said if that happens he will put a constitution (probably of his own devising) directly to the voters in a referendum.
Mr. Yeltsin's supporters are betting that he will emerge from the Congress even stronger than ever. But one of his allies, Sergei Shakhrai, said that, Russian politics being what it is, Mr. Yeltsin "should be prepared for any turn of events."