An aging, ailing leader cancels his schedule and heads for the hospital, while a scheming younger rival undercuts his authority and exposes his weaknesses. A familiar Moscow scenario, but played now with a twist: Prime Minister Yevgeny Primakov (69) stars in the former role, and President Boris Yeltsin (68) in the latter.

Primakov canceled a trip to Ukraine and several meetings in Moscow before checking into a local hospital for treatment for severe back pain. Maybe it’s the daggers.

Ten days ago, Yeltsin, speaking to regional leaders, said of Primakov: “Today he’s useful. Tomorrow we’ll see.” Primakov himself recalled that remark in a defensive televised speech in which he protested yet again that he has no presidential ambitions. When he took over as prime minister last September, he said, Russia faced hyperinflation, bankruptcy and “open, possibly bloody confrontation” between the president and the Duma. Now stability has been restored.

Well, maybe. But last week Yeltsin saw Primakov as less than useful in the diplomatic role in which, as a former foreign minister, he might be expected to excel. In a clear affront to Primakov’s position, Yeltsin named former Prime Minister Viktor Chernomyrdin, whom he called “a strong and wise man,” his personal representative on Yugoslavia.

That Chernomyrdin, a declared presidential candidate, can actually contribute anything at all to a settlement of the crisis in the Balkans is doubtful. On the positive side, he has not joined the majority of Russian politicians in their violent denunciations of Western motives and behavior, and his statements since his appointment have been relatively moderate. But even though Yeltsin insists that Chernomyrdin enjoys “prestige abroad,” he has in fact no particular claim on the attention of either the NATO allies or the Serbs.

Domestic political considerations aside, Chernomyrdin’s assignment seems a kamikaze mission at worst, an empty gesture at best. Ever since Western efforts to shove peace down the throat of Slobodan Milosevic failed in Paris last month, an early negotiated resolution to the Kosovo crisis has seemed impossible. But Russia, which backed the Rambouillet agreement that Yugoslavia rejected, is still playing the diplomatic game. A strange game it is right now, with only one player, but if Serbia’s stomach for self-immolation turns out to be no stronger than NATO’s stomach for war on the ground, all parties could get back in the diplomatic arena in a hurry. Should that happen, Chernomyrdin is likely to find himself on the sidelines again.