The United States and some 50 other countries have recognized Guaido as the legitimate leader of Venezuela, arguing that Maduro's re-election past year was invalid - partly because popular opposition candidates were barred from running. He visited several Latin American countries to lobby for global help. They don't know how to respond to Venezuela's people.
The pressure is just beginning.
Maduro, speaking for the first time since Guaido's return, said he would not allow "anything or anyone to disrupt the peace".
Just before his arrival, U.S. vice president Mike Pence sent a warning to Maduro to ensure Guaido's safety, and secretary of state Mike Pompeo later hailed his 'safe return'.
"We are going to defeat them, be absolutely sure", he said during a ceremony to commemorate the sixth anniversary of the death of his predecessor Hugo Chavez.
When he returned to Caracas - his latest challenge to Maduro's authority - Guaido announced to tens of thousands of supporters his plans for new protests. He then sped to a march where he mocked the government for letting him in so easily, telling the crowd: "Somebody didn't follow an order".
"In every democratic transition in Latin America there are negotiations, but I just would say it is extremely hard to see how he could play a positive role in a democratic election, " Abrams said. He became president seven years later.
The US is already trying to cripple Maduro's access to finances via sanctions on state oil company PDVSA and handing control to Guaido of Venezuelan bank accounts in the United States. Those who remain grapple with food and medicine shortages as President Nicolás Maduro refuses to give up his authoritarian regime and let humanitarian aid into the country. "It is extremely hard to see how he could play a positive role in a democratic election", he said, adding that it was ultimately up to Venezuelans to decide Maduro's future role.
"We haven't done that yet, secondary sanctions, it's clearly a possibility", Abrams said on Tuesday.
"The public administration is practically paralyzed". He has called on state officials, who have been historically pressured by the ruling Socialist Party to publicly back Maduro, to disavow the government, and has promised future amnesties for those that do. He urged state workers to prepare for a strike, though no date was given and he said an immediate priority will be to promote a law guaranteeing rights for public workers.
"The moment has arrived and our call, our request, and our complete support for public employees, is to bring about this strike", Guaido told a news conference after meeting with state workers.
During his travels, Juan Guaido met US Vice President Mike Pence and the leaders of Colombia, Brazil, Argentina, Paraguay, Chile and Ecuador.
In the same meeting, Russia's Ambassador to the UN Vassily Nebenzia accused Washington of seeking to topple President Maduro through military intervention, adding that the U.S.' policy toward Venezuela is tantamount to violating global law.
The high command has professed absolute loyalty to Maduro, however, and troops have blockaded border crossings to prevent the entry of humanitarian aid, supplied mostly by the United States.