She probably played only a minor role in last week’s government shake-up. According to her friends, Dyachenko shared her father’s view that the prime minister, Viktor Chernomyrdin, was becoming entirely too presidential. Tatyana doesn’t shrink from high-level firings. The turning point of the 1996 presidential campaign came when she helped persuade her father to sack several Kremlin hard-liners, including his unpopular chief bodyguard and drinking buddy, Aleksandr Korzhakov, who reportedly wanted Yeltsin to cancel the election. Later, Dyachenko endured a whispering campaign by political enemies, who spread untruthful rumors that she was having an affair with Anatoly Chubais, Yeltsin’s top economic reformer at the time.

Trained as a mathematician, Dyachenko is methodical, rational and calm–a sharp contrast to her willful and capricious father. Only four years ago she was tracking missile trajectories at the Salyut space center and looking after her husband, Aleksei, an aerospace engineer, and her son from a previous marriage, Boris, now 16, Yeltsin’s favorite grandson and namesake. Then, in the re-election crisis of 1996, she became her father’s unofficial image manager, dressing him for the campaign in a cuddly sweater and ordering his security guards to take off their sunglasses so they wouldn’t look so thuggish. Now young Boris has been packed off to a fancy boarding school in Britain while his mother works full time deciding who gets to see the man she addresses as ““Papa.’’ The president seems to respect her judgment about personnel. Aleksandr Lebed, the popular former general who worked for Yeltsin and then was fired, says resentfully: ““Tatyana has set up a very clever scenario: “Only trust the people I trust’.''

Dyachenko performs another critical function in Yeltsin’s administration: she’s a one-woman anti-alcohol police force, constantly trying to make sure her father stays away from his beloved vodka. That’s one reason she has become a familiar sight on the president’s trips abroad; in the past he used foreign excursions as an excuse to go on a bender. And since he is still extremely frail, she makes sure he follows his doctors’ orders and gets plenty of rest. Yeltsin appears to accept her ministrations–believing, evidently, that Daughter Knows Best.