CARACAS, Venezuela, Nov. 29 — Three days before a referendum that would vastly expand the powers of President Hugo Chavez, this city’s streets were packed with tens of thousands of opponents to the change on Thursday, a sign that Venezuelans may be balking at placing so much authority in the hands of one man.
Even some of Mr. Chavez’s most fervent supporters are beginning to show signs of hesitation at supporting the constitutional changes he is promoting, including ending term limits for the president and greatly centralizing his authority.
New fissures are emerging among his once-cohesive supporters, pointing to the toughest test at the polls for Mr. Chavez in his nine-year presidency.
In the slums of the capital, where some of the president’s staunchest backers live amid the cinder block hovels, debate over the changes has grown more intense in recent days.
“Chávez is delirious if he thinks we’re going to follow him like sheep,” said Ivonne Torrealba, 29, a hairdresser in Coche who supported Mr. Chávez in every election beginning with his first campaign for president in 1998. “If this government cannot get me milk or asphalt for our roads, how is it going to give my mother a pension?”
Both Mr. Chávez and his critics say opinion polls show they will prevail, suggesting a highly contentious outcome. For the first time in years, Venezuela did not invite electoral observers from the Organization of American States and the European Union, opening the government to claims of fraud if he wins.
Violence has already marked the weeks preceding to the vote. Two students involved in antigovernment protests claimed they were kidnapped and tortured this week by masked men in Barquisimeto, an interior city. And in Valencia, another city, a supporter of Mr. Chávez was shot dead this week in an exchange of gunfire at a protest site.
Tension has also been heightened by rare criticism of the constitutional overhaul from a breakaway party in Mr. Chávez’s coalition in the National Assembly and former confidants of the president, and the government has reacted to this dissent by describing it as “treason.”
Meanwhile, Mr. Chávez and senior officials here have exhibited increasingly erratic behavior ahead of the referendum. Mr. Chávez has lashed out at leaders in Colombia and Spain and asked for an investigation into whether CNN was seeking to incite an assassination attempt against him.
Reports of such plots are not in short supply here. State television also broadcast coverage this week of a memorandum in Spanish claimed to be written by the C.I.A. in which destabilization plans against Mr. Chávez were laid out. A spokesman for the United States embassy here was unavailable for comment on the report.
Other analysts, including investigators who had previously uncovered financing of Venezuelan opposition groups by the United States government, expressed doubts about the authenticity of the memo, dubbed by Venezuelan officials as part of a plan called “Operation Pliers.”
“I find the document quite suspect,” said Jeremy Bigwood, an independent researcher in Washington. “There’s not an original version in English, and the timing of its release is strange. Everything about it smells bad.”
The simple home of Ms. Torrealba, the hairdresser, located near open sewage alongside a deafening highway in southwestern Caracas, is a case in point. Last December, she and her siblings awoke at dawn with fireworks to celebrate Mr. Chávez’s re-election to a six-year term, which he won with 63 percent of the vote.
This year, the mood in Ms. Torrealba’s home is glum. Her sister, Yohana Torrealba, 20, said she was alarmed by what she viewed as political intimidation by teachers in Misión Ribas, a social welfare program where she takes remedial high-school-level courses.
“The instructors told us we had to vote in favor and demonstrate on the streets for Chávez,” Yohana Torrealba said. “They want Venezuela to become like Cuba.”
Throughout the slums of Coche, confusion persists about how life could change if the constitutional changes are approved. Many residents who own their homes, however humble they may be, fear the government could take control of their property, despite efforts to dispel those fears by Mr. Chávez’s government.
Others wonder what will happen to the mayor and the governor they elected if Mr. Chávez wins the power to handpick rulers for new administrative regions he wants to create. Still others said they were afraid of voting against the proposal out of concern the government could discriminate against its opponents if their vote is made public.
But Mr. Chávez also commands an unrivaled political machine, with his supporters controlling every major institution of government and the loyalty of many voters in Coche and elsewhere. “It’s a lie that they’re going to take our houses away,” said Yanelcy Maitán, 40. “No one has done more for the poor than Chávez.”