On Monday, July 31, Fidel Castro's secretary read a letter in which the 79-year-old Cuban dictator temporarily purports to delegate authority to his brother Raúl Castro, first vice president of the Council of State and minister of the armed forces. Apparently stress from the dictator's recent trip to Argentina for a Southern Cone Common Market meeting resulted in intestinal bleeding and an operation to stop it.

Cuban Americans in Miami, as well as democrats around the world, hope the incident may hasten a change in power on the island prison. However, it's probably too soon to break out the bubbly. Fidel has already proven himself a survivor in his old age - having overcome periods of incoherence and broken bones when he fell into metal folding chairs. Plus his brother could be just as nasty.

What's certain about Cuba's future is that it's hard to predict. The demise of one or both Castros could lead to a power struggle among senior leaders, a collegial junta of generals ready to sustain control over Cuba's major income-generating enterprises (such as tourism), or a loss of control over the masses.

Twenty years ago, U.S. policymakers thought change depended on an end to $5 billion-a-year Soviet subsidies. When the Soviet Union collapsed in 1991, cash-starved Cuba weathered the crisis through tourism and by allowing limited self-employment to citizens for whom the state couldn't provide jobs.

In case of death, Raúl, the 79-year-old dictator's younger brother by four years, is the designated successor. He is reportedly melancholy, uncharismatic, and in questionable health himself. Moreover, he is believed to admire China's slow transition toward capitalism, leading some analysts to think he might be a malleable, temporary figure.

Yet, Raúl has always been Fidel's dour enforcer, arranging for killings and imprisonments. He is the architect of the current Cuban Communist party and organs of civilian government. As long as Fidel is living, he is unlikely to make any changes. And even if Fidel goes to eternal justice soon, Raúl may be expected to extend the regime's iron rule for some time with support from the Cuban Revolutionary Armed Forces.

With the death of either brother, a growing number of dissidents and human-rights activists on the island may feel emboldened to press for political freedoms. In 2002, Oswaldo Payá's Varela Project petitioned the regime to reject socialism. A year later, Payá unveiled a Plan for a National Dialogue - a roadmap to elections and a mixed economy. Last year, an unprecedented dissident assembly took place in Havana. However, these activists penetrated by state spies and weakened by an apathetic population accustomed to harsh rule.

Since Castro came to power in 1959, the United States has had few cards to play. Short of military action, no U.S. policy would (or will) force change. Such policies must tread a thin line between gaining influence by dealing with the regime on its terms and being true to Cuban citizens pressing for freedom. Still, there are ways to influence the decline of Castro's revolution, but they depend on timing and patience.

Some useful analysis has already been done. The Bush administration's Commission for Assistance to a Free Cuba last year produced a comprehensive 400-page report on what Cuba's economy, infrastructure, and society would need in the event of a transition toward democracy. This year's report builds on that database.

But hastening a transition is the hard part. Partial trade sanctions exist alongside aid to dissidents such as independent journalists, librarians, and human-rights activists. What's missing is a simple, clear set of incentives for a post-Castro government to adopt democratic and free-market reforms and one which encourages follow-on leaders and the Cuban people to put non-Communists into the government.

The current message to Cuban leaders is: No normal ties until the Castros are gone and there is democracy and free markets. Not easily done from one day to the next. Incentives should be more detailed and recognize baby steps: basic trade relations when ordinary Cubans may establish and run their own businesses, diplomatic ties when Cuba celebrates competitive elections and guarantees certain civil liberties, and no more travel restrictions when Cubans may travel freely and work where they wish. Such principles should be communicated to Cuba's leaders, and frequently broadcast to its citizens over U.S.-sponsored Radio and TV Martí.

For now, does Castro's latest health crisis signal springtime for Cuba? Maybe. But even if it is the dictator's last gasp, there's still a bumpy road ahead. And if the old bully hangs on, you can bet he loves all the attention.

Stephen Johnson is senior policy analyst for Latin America in the Davis Institute for International Studies at The Heritage Foundation.