When President Bush declared last week that political openness naturally accompanied economic openness, his counterparts in Beijing and Moscow were not the only ones to object. Liberal and conservative intellectuals, even once ardent supporters, have backed away from the century-old theory that democracy and capitalism, like Paris Hilton and paparazzi, need each other to survive.

From China, where astounding economic growth persists despite Communist Party rule, to Russia, where President Vladimir V. Putin has squelched opposition, to Venezuela, where dissent is silenced, developments around the world have been tearing jawbreaker-size holes in what has been a remarkably powerful idea, not only in academic circles but also in both Republican and Democratic administrations — that capitalism and democracy are two sides of a coin.

“People, including myself, still have reasons to think it will eventually happen,” Francis Fukuyama, a political economist at the Johns Hopkins School of Advanced International Studies, said of China’s evolution to democracy. “But the time frame has to be a lot longer.” At least in the next couple of decades, he said, it is likely that “the authoritarian system will keep going and get stronger.”

Mr. Fukuyama, perhaps more than anyone else, has been associated with the idea that capitalism and democracy are inextricably linked. In his famous essay, “The End of History,” written in 1989 as the Soviet Union was in decline, he declared that all nations would ultimately develop into Western-style liberal democracies.

“There was great hope in the early 1990s,” said Michael Mandelbaum, the author of the forthcoming book “Democracy’s Good Name: The Rise and Risks of the World’s Most Popular Form of Government.” The belief was that rising incomes would create a middle class that would agitate for personal liberty and political power. The tipping point seemed to occur when per capita income reached somewhere between $6,000 and $8,000. True, there were exceptions like tiny Singapore with its growing wealth and one-party state, but they were often dismissed as too small or transitional to really put a dent in the theory.

Yet, as the free market and autocrats gained power in the Caucasus, Central Asia, Latin America and Russia, the initial optimism about democracy’s sure-footed march faltered. Some scholars pointed out that the American experience, where democracy and capitalism arose at the same time, was not so much a model for the rest of the world as an anomaly. “Capitalism came before democracy essentially everywhere, except in this country, where they started at the same time,” said Bruce R. Scott, an economist at Harvard Business School who is finishing a book titled “Capitalism, Democracy and Development.”