The administration has focused intensely on Venezuela in recent months, naming a special envoy, dispatching Pence and others to give speeches and rally the world to unite against Maduro’s government, which has styled itself as socialist but bankrupted the country’s economy through mismanagement and graft.

But momentum has lagged since pro-Maduro military forces stopped a high-profile, U.S.-led effort to deliver humanitarian aid to Venezuelans in late February, causing fatalities. And regional leaders have since dismissed calls from Venezuela’s opposition to consider using force against Maduro…

Some analysts say Maduro, who has support from Russia and Cuba, could hang on for years. After all, the U.S. has “been promising [regime change] to the Cubans in Miami for 60 years,” noted Ted Piccone, a Latin America specialist at the Brookings Institution.

“Authoritarian governments don’t give up easily,” added a Senate aide. “They don’t wake up one day and say, ‘Wow, John Bolton’s tweet was so intimidating I’m going to pack up my things and leave the country.’”