Does socialism have a future? Cuba will vote on a new constitution and decide on whether socialism has a future. They are expected to turn up in millions and finally come up with an answer. The document updates its Cold War-era predecessor, the original 1976 charter enacted under Fidel Castro, and the vote is widely seen as an important referendum on Cuba's entire single-party, socialist system. All this after US President Donald Trump claimed earlier that "socialism was dying" and described Cuba as a "captive nation." Cuban officials promptly exhorted the population to vote yes to the constitution as a matter of patriotism. Cuban President Miguel Diaz-Canel said a "yes" vote was "a mobilisation for peace and against imperial intervention in Latin America." If passed, Cuba's updated constitution would protect private property, reintroduce the role of prime minister and, for the first time, limit the Cuban presidency to two consecutive five-year terms. Championed by Raul Castro, brother and successor to Fidel, the document is hoped to enshrine the fundamentals of Cuba's existing political system for the next generation. Anything but a wide margin of victory would be viewed as a rare rebuke of the communist-run government's policies. The state controls all the TV, radio and newspapers on the island, and none has reflected any viewpoint supporting a "no" vote. Across the island, government supporters have placed signs on buildings, doorways and school buses urging people to vote for the constitution, while there have been few public displays supporting a "no" vote. But in a significant development, dissident groups have complained they are blocked from campaigning against the constitution. "They attack those of us who call on the people to 'no,'" said Jose Daniel Ferrer, the leader of anti-government dissident group UNPACU, the acronym for the Patriotic Union of Cuba, in a video posted on his Twitter account. He says his group is planning to go on a hunger strike to protest physical intimidation and arbitrary arrests by Cuban authorities. The government organised thousands of meetings for citizens to suggest modifications to the constitution. Some voters have exercised their influence already, following a backlash by conservative religious groups, the government backed off language that would have legalized same-sex marriage in the constitution. The vote presents a rare opportunity for Cubans to express the kind of dissent that some government supporters still consider treasonous. Government officials say the vote is secret, and have promised that Cubans who vote no or deface or leave their ballots blank, will not face retaliation. However, the official line remains that voters should approve the new charter even if they don't agree with all its proposals. The result is a foregone conclusion.