MOSCOW -- The political pulling and tugging that is shaping the future of the Soviet government took a dramatic turn yesterday when Eduard A. Shevardnadze, the respected former foreign minister, said that he has quit the Communist Party.
In doing so, he makes it considerably less likely that President Mikhail S. Gorbachev can successfully refashion the party to keep the reform movement within its embrace -- and considerably more likely that an independent party will arise to challenge the Communists.
Mr. Gorbachev himself warned last week that if Communist hard-liners drive reformers out of the party, it will be "doomed" come election time.
Mr. Shevardnadze made it clear yesterday that he was quitting because of attacks from hard-liners. On Monday, he was summoned to appear before a party commission to explain his support for reform.
"Under no circumstances will I agree to be brought as a defendant before this 'kangaroo court,' " he replied in a letter released yesterday by the Soviet Interfax news agency.
Instead of showing up, Mr. Shevardnadze quit the party.
His move also comes at a critical time for the reform movement itself. A struggle is going on between those who seek a broad-based national movement that could overlap the liberal wing of the Communist Party and those who say that the Communists have had their chance and it's time for a new party.
Nine reformers -- including Mr. Shevardnadze as well as some top aides to Mr. Gorbachev -- signed a declaration earlier this week urging a unified democratic reform movement, and were )) greeted with moderate praise from Mr. Gorbachev.
Some later said they hope the movement can help to encourage and strengthen Mr. Gorbachev's liberal tendencies.
But several of those signing the declaration would prefer to turn that movement into an independent party in September, one that would be in direct opposition to Mr. Gorbachev. Yesterday's news of Mr. Shevardnadze's resignation only strengthened their hand.
They also won key support yesterday from Boris N. Yeltsin, the ex-Communist and president-elect of the Russian Federation. Although he has been getting along well with Mr. Gorbachev for the past month, Mr. Yeltsin not only endorsed the democratic reform group's effort but said he favored the creation of a new party dedicated to radical reform.
In the past, Mr. Shevardnadze -- a full member of the Communist Party Politburo until July 1990 -- has said he would welcome a two-party system in the Soviet Union.
For his part, Mr. Gorbachev has been tacking strongly to the liberal side ever since the spring (although sporadic provocative acts by security forces in the non-Russian republics have continued). In the face of Mr. Yeltsin's overwhelming victory in the Russian elections in June, when he swamped Communist opponents, Mr. Gorbachev has been turning up the heat on those hard-liners insisting on party purity.
As head of a monolithic, right-wing party, Mr. Gorbachev would appear to have little chance of actually winning an election.
A Communist Party meeting scheduled for the end of July seemed to offer the chance for a general realignment away from the hard-liners. But Mr. Shevardnadze's resignation raises the possibility that the reformers may jump first.
Mr. Shevardnadze is the former party chief in Georgia, where he had a reputation for fighting ruthlessly against both corruption and dissent. But when Mr. Gorbachev made him foreign minister, he became one of the leading proponents of reform and played a major role in ending the Cold War.
He abruptly resigned in December, warning of dictatorship, less than a month before the Soviet army killings in Lithuania. Now, just two weeks before Mr. Gorbachev heads for London to plead his case for aid from the Western nations, Mr. Shevardnadze is warning once again.
It came at a sweltering news conference Wednesday at Moscow City Hall, when several of the signers of this week's reform document attempted with some success to answer questions from the news media and with less success to keep from disagreeing with each other.
Mr. Shevardnadze, with a barely audible voice, his brilliant white hair shining as he sat beneath a golden hammer and sickle, said the democratic opposition group was coming into being in order to bring to an end once and for all "the threat of dictatorship."