CARACAS — Critics called it ‘‘zero hour’’ for Venezuelan democracy, a tipping point into dictatorship. But after the socialist government here held a widely condemned election on Sunday, the opposition in this teetering South American nation faced an existential question.

What next?

The Trump administration on Monday slapped financial sanctions on President Nicolas Maduro.

The sanctions freeze any assets Maduro may have in US jurisdictions and bar Americans from doing business with him. They were outlined in a brief notice by the Treasury Department’s Office of Foreign Assets Control ahead of a White House announcement from President Trump’s national security adviser H.R. McMaster and Treasury Secretary Steven Mnuchin.

McMaster described the election, which creates a constituent assembly that will rewrite Venezuela’s constitution, as an ‘‘outrageous seizure of absolute power’’ that ‘‘represents a very serious blow to democracy in our hemisphere.’’

‘‘Maduro is not just a bad leader, he is now a dictator,’’ McMaster said.

To the blaring sounds of salsa in the central Plaza Bolivar, Maduro late Sunday lauded the vote creating a new super congress made up entirely of government backers, including his wife and son.

As early as Tuesday, members of the new Constituent Assembly are set to replace the democratically elected legislators inside this nation’s National Assembly building.

Maduro has said he proposed the new assembly to bring peace after four months of often-violent demonstrations protesting the collapse of the economy and growing authoritarianism.

Opposition leaders are facing their own test of public confidence in the wake of Sunday’s vote. ‘‘Today I feel crushed, but not because of the results, because we knew that the government would cheat,’’ said Victoria Daboin, a 25-year-old who has been protesting since April. ‘‘I feel depressed because today everything looks normal, as if nothing had happened. The streets are empty and people went to work as if nothing ever happened. I personally expected more forceful actions from opposition leaders.’’

A top contender, opposition leader Leopoldo Lopez, remains under house arrest and sidelined from public activities. In recent days the opposition has seemed disorganized, caught flat-footed by a government announcement banning protests through Tuesday.

For the opposition, there appears, as of yet, to be no agreement on which tactic going forward is best.

Material from the Associated Press was used in this report.