As Cuban-American economist Carmelo Mesa-Lago observed in March, Castro’s Cuba has been a dependency for 60 years. The Soviet Union poured $65 billion into the island from 1960-90. With the dissolution of the Soviet empire, aid to Cuba dried up and the 1990s were an extremely difficult period. But Venezuela picked up the subsidy slack when Chávez came to power in 1999. “At its peak in 2012, Venezuelan aid, subsidies and investment amounted to $14 billion, or close to 12% of gross domestic product,” Mr. Mesa-Lago wrote.

“Cuba is now facing its worst economic crisis since the 1990s,” Mr. Mesa-Lago explained. It refuses to reform its sclerotic economy—because economic power gives way to political power. Now its Venezuelan sugar daddy is cutting back on aid. Oil shipments to the island have been halved in recent years, and Caracas no longer has unlimited resources to pay the Castro regime for the tens of thousands of Cuban doctors, teachers, sports trainers and managers of ports and airports—not to mention security forces—in Venezuela.

Things will go from bad to worse for Havana if Mr. Guaidó is allowed to hold elections. This is why the Cubans are ruthlessly cracking down on the opposition while making the absurd proposal to the Lima Group that Havana ought to mediate a compromise solution. As if the fox ought to decide the fate of the hens. Defectors repeatedly testify that Cubans are behind the Venezuelan police state. It’s why the U.S. and its allies must shift their focus to Havana.