As he struggles to overcome double pneumonia, even his admirers privately concede that Mr Yeltsin will soon be forced to acknowledge that he is no longer well enough to remain in charge of the largest country on the planet.
More than six months have elapsed since he was re-elected for his final term; he has been absent for most of that time. Although he may well recover from his present illness, few expect him to complete his full term. He is ill, worn out and, by Russian standards, old - seven years above the average male life expectancy.
The mood is hard to pinpoint with facts, yet it is palpable. When Mr Yeltsin had yet another bout of heart trouble last summer, his entourage was bullish, angrily debunking reports that he could not work more than 15 minutes a day. The president was beavering away on documents, they insisted.
This time, there is far more gloom. The Kremlin's spokes-man, Sergei Yastrzhemsky, is going through the paces, reassuring the world that his boss is getting better. But the Kremlin doctors have sounded increasingly wary. What was described 10 days ago as "early signs of pneumonia" is now referred to as double pneumonia triggered by bronchitis, an "unpredict- able" condition that can bring complications later on.
Once-loyal newspapers that kept quiet about Mr Yeltsin's health during his election campaign now sound alarmed. An editorial in Izvestia described him as "clearly seriously ill" and expressed concern about the stability of the country. When the prime minister, Viktor Cherno-myrdin, declared yesterday that Russia's reforms would continue, he was almost assuming the absence of Mr Yeltsin.
And there are signs that the political establishment is pre-paring for life after Boris. For instance, a debate has begun about whether the Russian constitution, forced into law by Mr Yeltsin in 1993, places too much power in the hands of one man. Consensus is growing in favour of the views of Yegor Stroyev, speaker of parliament's upper house and a staunch Yeltsin supporter, who has called for an amendment giving more power to parliament, arguing that "the constitution is not an icon".
Mr Stroyev's concern is not that his friend, Mr Yeltsin, will abuse his powers. What worries him, and many others, is the use to which they may be put by his successor. Looming ominously into view is Alexander Lebed, the former paratrooper general who is the favourite to win an election if one were called soon.
If there is one Russian who appears confident that Mr Yeltsin is about to exit, it is Mr Lebed. In the three months since he was sacked as national security adviser, after securing a peace deal in Chechnya, his appetite for the presidency has grown sharper. When he dis-covered Mr Yeltsin was bed-ridden again, he moved his cam- paign up a gear, calling repeatedly for the president to quit. "I want to become president, and I will," he announced, before setting off on a trip to Germany.
Having lost badly to Mr Yeltsin, the Communists and nationalists do not want to be humiliated at the ballot box, especially by someone who could take their grassroots vote. Many in government do not relish a president who threatens to root out official corruption, and take control of foreign trade - a source of many fortunes.
Should an election be called, the Kremlin would almost certainly try to throttle Mr Lebed's media access and throw money at their chosen candidate. But the general would still have a strong chance of victory, especially if he were perceived by the public as a victim of the establishment. "Every segment of the Russian political elite would stand to lose a great deal if Lebed were to win ... an election," wrote Andrei Piontkow-sky, head of Moscow's Centre for Strategic Studies, in theMoscow Times.
It is for this reason that the Communist-dominated lower house of parliament has been quietly building bridges with the prime minister, Viktor Chernomyrdin, cooperating with his move to pass a federal budget. It is also no coincidence that an ardent political enemy of Mr Yeltsin, Oleg Rumyantsev, has floated the idea of another constitutional amendment - a law allowing prime minister Viktor Chernomyrdin to stand in for the sick president for 18 months (instead of the current three) before calling an election. The apparatchiks who run Russia hope that, by then, Mr Lebed will be forgotten.