MOSCOW, MAY 25 -- Soviet President Mikhail Gorbachev's favored candidate for the presidency of the Russian republic dropped out of the race today just before the vote, and the Kremlin threw its support behind a hard-line conservative to beat radical populist Boris Yeltsin.

The surprise withdrawal by Alexander Vlasov appeared to reflect Gorbachev's calculation that he needed another candidate to prevent his rival Yeltsin from winning the important post. The Communist Party faction in the republic's parliament is now backing Ivan Polozkov, the party chief of Krasnodar in southern Russia.

{Yeltsin finished first in the balloting but failed to gain enough votes to win, Reuter news agency reported, quoting parliamentary sources. Yeltsin received 497 votes to Polozkov's 473, with 34 abstensions. Since no candidate in the four-way race received a majority of votes, a second poll will be held, probably Saturday.}

Deputies say Yeltsin has about a 50 percent chance of winning.

Polozkov is much more conservative than Vlasov, the Russian republic's prime minister. Many deputies considered Vlasov, a junior member of the Communist Party Politburo, to be a bland alternative to Yeltsin. Vlasov gave no reason for withdrawing from the race.

Gorbachev's backing of Vlasov, and now Polozkov, is further evidence that he is usually more comfortable with conservative party politicians than radical independents. Gorbachev is especially wary of Yeltsin, who has been attacking party leaders since he was dropped from the leadership in late 1987.

In an emotional speech in the Russian parliament this week, Gorbachev attacked Yeltsin for failing to support socialism and for trying to "tear apart the union."

If Yeltsin does win the Russian presidency, he would gain an important base as leader of the Soviet Union's biggest and most essential republic. Yeltsin said that despite his differences with Gorbachev, he was prepared for "businesslike relations, negotiations and dialogue."

Yeltsin said he favored radical reform of the economy but added, "I differ from the central government in one important respect -- I'm not for reforms that impoverish the people." The remark was obviously a swipe at the leadership's latest package of reforms, which call for higher food prices.

Asked about Gorbachev's ideological attack on him, Yeltsin said, "I am not for socialism for socialism's sake."

Polozkov said he had "great respect" for the most conservative member of the Communist Party Politburo, Yegor Ligachev. Polozkov said the country was not yet ready for a market economy, adding, "We made a socialist choice and we should stick to it."