Vladimir Putin is a former KGB spy, a shrewd bureaucratic operator - and a completely untested public politician.
He also has the reputation of a man who is completely loyal to his immediate boss.
In a televised address Monday, Yeltsin said that Putin was the man who would unite the country, consolidate economic reforms and lead Russia into the new millennium. "He will be able to unite those who will renew Russia's greatness in the 21st century," said President Boris Yeltsin.
But analysts say that Putin, an uninspiring speaker who rarely makes public statements, would be a tough sell in Russia's presidential elections, scheduled for next July.
"I can't imagine that in one year's time it will be possible to turn Putin into a viable public politician," said Yevgeny Volk of the conservative Heritage Foundation's Moscow office. Instead, said Volk, "Putin will be a useful and obedient tool in Yeltsin's hands."
Putin, nominated for prime minister on Monday after Yeltsin fired Sergei Stepashin, has been director of the Federal Security Service, or FSB, the main successor agency to the Soviet KGB, and has chaired the Security Council, which advises the president. His views on important matters such as economic policy are not well known.
Several observers said that Stepashin was sacked in favor of Putin because Putin is a tougher operator, more likely to use all available means against Yeltsin's opponents - Gennady Zyuganov's Communists, Moscow Mayor Yury Luzhkov, and Russia's increasingly assertive regional leaders.
Throughout his career, Putin has been a tough bureaucratic infighter and a master of behind-the-scenes politics who has been able to advance his career and loyally serve various masters.
After graduating from Leningrad State University in 1975 with a degree in law, Putin served 15 years in the KGB's foreign intelligence wing and served tours of duty in East Germany.
In 1990 he began working in St. Petersburg's local government as an aide to Anatoly Sobchak, mayor from 1991 until 1996, - where he earned the nickname of Sobchak's "grey cardinal," wielding enormous behind-the-scenes influence. He chaired government meetings during Sobchak's frequent absences and oversaw the city's relations with foreign governments.
After Sobchak's defeat at the polls in June 1996, Putin's career took a meteoric rise. Following Yeltsin's re-election, Putin - reportedly at the urging of Anatoly Chubais, then Kremlin chief of staff - was brought to Moscow to work in the Kremlin. In March 1997, he was named chairman of the Kremlin's General Control Office, a watchdog body charged with fighting corruption and overseeing the implementation of presidential decrees.
In that job, Putin took a tough line with Russia's regional governors who were straying too far from the Kremlin line.
Last July, Yeltsin appointed Putin FSB director, replacing Nikolai Kovalyov. He pushed criminal cases against local leaders in Yekaterinburg and St. Petersburg.
Although Putin is widely viewed as a liberal - at least by secret police standards - on his watch, the FSB prosecuted environmentalists Alexander Nikitin and Grigory Pasko, naval officers accused of espionage for exposing the Russia military's slipshod handling of nuclear waste.
And since he has served as its director, the FSB has also protected the Kremlin's political interests. In April, for example, as the State Duma was debating Yeltsin's impeachment, Putin's FSB sent an "analytical document" to both houses of parliament, claiming that the articles of impeachment contained "significant mistakes of a legal nature."
The document was widely seen as an attempt to threaten lawmakers with the use of force should they try to remove Yeltsin.
In the Vladimir region, the FSB and the Prosecutor General's Office opened a criminal investigation that led to investigators examining bank accounts of the Inteko plastics company, which is owned by Yelena Baturina, the wife of Moscow Mayor Luzhkov.
On Monday, Putin denied any political motivation in the matter.
"Security officers did not know that the wife of the Moscow mayor headed one of those companies," said Putin, adding that there is "no reason to believe that she personally broke the law."