But last night, his comeback was in tatters after he was rushed by helicopter from a country residence to Moscow's Central Clinical Hospital, evidently exhausted by his summit meetings in France and the United States. He had suffered another heart attack, his second in less than four months.
Although he has yet to announce his candidacy for next year's election, his illness will certainly damage his chances of re-election to the Kremlin's top job. He already faces a disgruntled electorate, worn down by rising prices, unemployment, a fruitless war in Chechnya and a growing perception that Russia no longer matters in global terms.
Now, when he least needs it, he has given Russian voters another jarring reminder that he is physically as well as politically weak. It is no surprise, then, that on the streets of Moscow, the news of his hospitalisation seemed to arouse only lukewarm interest.
Last night, as news of his illness spread, speculation turned to what would happen if he proves to be incapacitated. Under the constitution, the reins of power would pass Viktor Chernomyrdin, the Prime Minister, who would run the country until the President recovered or an election was held.
Whatever Mr Yeltsin's current problem (and it was reportedly only a mild heart attack) his inner circle may decide to do nothing, just as they did when he had a heart attack this summer. Although his condition turned out to be far more serious than the Kremlin initially admitted, his staff went to elaborate lengths to convince the world that he was still at the helm. This back-fired badly when a sharp-eyed photographer noticed that the same print had been released several months earlier.
Last night, his staff were anxiously awaiting a medical diagnosis to confirm his ailment, which is believed to be ischaemia - which affects the blood supply to the heart. The President has never been able to dispel rumours that he has a drink problem, although his aides deny it. His conspicuously high spirits in New York, and his rather puffy features, aroused new suspicions.
Alleged drinking exploits aside, he has a serious medical condition which has plagued him since before he became President. In November 1987, he was taken to hospital with chest pains after being dumped as the head of the Moscow Communist Party. In April 1990, he was back in hospital with what his aides described as "possible" heart problems. The following year he spent two weeks recuperating on the Black Sea after more suspected cardiac trouble.
For all this, long-term observers of Mr Yeltsin were cautious yesterday. Whatever his problems today, there is much water to flow under the bridge before next June, including parliamentary elections in December. He has a remarkable habit of bouncing back. "If he is not seriously ill he will run again," said the political commentator Sergei Chujaev. "Power is like a narcotic with him. He can't live any other way."