Over the years, Raúl has steadily taken on more state responsibilities. But he does not share widespread support among the general population, experts say, because they view him as brutal, after the hard line he is believed to have taken with his enemies in the early days of the revolution. Most of his support comes from the military, which he has run for over 45 years.
"He does not occupy the same place in the historiography of the Cuban Revolution as his brother," says Mark Falcoff, author of "Cuba, the Morning After." "But you don't have to be popular to be a dictator."
Raúl's economic vision is where most see room for change after Fidel. The military has largely been handling tourism, which requires foreign investment.
When the subsidies of the Soviet Union disappeared with its collapse in 1991, it was Raúl who urged the opening up of incentives to farmers to be able to sell surplus goods to local markets, reforms which have been scaled back in recent years. Many say he would likely reinstitute and expand such measures.
"If Raúl Castro introduces some sort of reforms or openings, even those that maybe are not that large," says Ian Vasquez, director of the Project on Global Economic Liberty at the libertarian CATO Institute, "those might be cracks in the system that are difficult to control, and may make it hard to hold Cuban socialism together."
This movement could be meaningless for better US-Cuba ties, however, if the US continues to refuse to deal with any member of the Castro team. A report issued recently on US plans in a post-Fidel Cuba pledged $80 million to bolster Cuban democracy. "Raúl is perfectly capable of bringing about some change," says Wayne Smith, a former US diplomat in Havana. "He is open to the idea of a constructive relationship with the US. But the Bush administration is not open to that at all."