The list of delegates includes powerful members of the president’s political movement, including Diosdado Cabello, a top lawmaker in the ruling Socialist Party who was involved in a failed coup attempt in the 1990s, and Cilia Flores, the president’s wife.
But the push to consolidate power also puts the country at a crossroads, one laden with risk.
As Mr. Maduro effectively steers his country toward one-party rule, he sets it on a collision course with the United States, which buys nearly half of Venezuela’s oil. On Wednesday, the Trump administration froze the assets of, and forbade Americans to do business with, 13 Venezuelans close to Mr. Maduro, including his interior minister and heads of the army, police and national guard.
The administration is warning that harsher measures could follow, with “strong and swift economic actions” if the vote happens on Sunday, according to Mr. Trump. In a statement, he called Mr. Maduro a “bad leader who dreams of becoming a dictator.”
There is also the potential powder keg on Venezuela’s streets. Infuriated by Mr. Maduro’s government, the opposition has mobilized more than three months of street protests that have crippled cities with general strikes, rallies and looting. More than 110 people have been killed, many in clashes between the state and armed protesters. Few know how protesters will react to newly imposed rulers.
Even the members of the new assembly themselves are a wild card. Their power will be so vast that they could possibly remove Mr. Maduro from office, some analysts note, ending a presidency that has been deeply unpopular, even among many leftists.
“It’s a crapshoot, a Pandora’s box,” said Alejandro Velasco, a Venezuelan historian at New York University who studies the country’s leftist movements. “You do this and you have so little control over how it plays out.”
Mr. Maduro contends that the government restructuring is necessary to prevent more bloodshed on the streets and save Venezuela’s failing economy, which is dogged by shortages of food and medicine.
The president has refused to negotiate with street protesters, calling some of them terrorists and asserting that they are financed by outside governments trying to overthrow him. A new governing charter would give him wide-ranging tools to “construct peace,” he and leftists have said.
“We need order, justice,” Mr. Maduro said during an interview with state television this month. “We have only one option, a national constituent assembly.”
The turmoil gripping Venezuela illustrates the sweeping declines in popularity for the Venezuelan left since the death of its standard-bearer, President Hugo Chávez, in 2013.
It was Mr. Chávez who oversaw the last rewrite of the Constitution, in 1999, which was widely backed by the voters who had propelled him to office in the belief that the country’s rule book favored the rich.
That new Constitution — and rising oil prices — fueled a Socialist-inspired transformation in Venezuela. It helped enable Mr. Chávez to redistribute state wealth to the poor, nationalize foreign assets and make him popular with his supporters. The Constitution also left open the possibility of another constituent assembly in the future.
Now Mr. Maduro has taken that option at a time when the leftists are dogged by their deepest crisis in decades. This time, Venezuelans are seeing it less as a stab at reform than as an attempt by a struggling ruling class to maintain power.
“It’s a last-ditch effort to secure his base,” Mr. Velasco said. “He’s doing it at a moment of weakness.”
Under the rules of the vote, the constituent assembly would take the reins of the country within 72 hours of being officially certified, though it is unclear to most people what would happen after that.
Some politicians have already suggested that governorships and mayors be replaced with “communal councils.” Top members of Mr. Maduro’s party have identified Luisa Ortega, the attorney general, who has criticized Mr. Maduro’s crackdown on protesters, as someone to be immediately dismissed.