Students helped make Thursday's rally, the official close of the campaign against Chavez's proposed constitutional changes, one of the largest to defy him in recent years.
There was no official count of legions of protesters that marched along Bolivar Avenue blowing whistles, waving placards and shouting "Not like this!" but opposition politician Leopoldo Lopez estimated 160,000 turned out to protest.
Venezuelans on Sunday vote on 69 proposed changes to nation's 1999 constitution that would, among other things, create forms of communal property, eliminate presidential term limits, and increase presidential authority.
Chavez, who has vowed his backers will triple Thursday's turnout in their own march on Friday, denies the changes are a bid for unchecked power. He contends they are necessary to give the people a greater voice in government through community-based councils.
Demonstrations for and against the revised amendments have surged across the country in the run-up to the vote, occasionally leading to clashes. There were no immediate reports of violence Thursday.
In just six months, university students have breathed new life into the country's fractured opposition, becoming the most potent source of resistance to Chavez's government.
Their movement first coalesced in May, when thousands of undergraduates took to the streets to angrily denounce Chavez's refusal to renew the broadcast license for Radio Caracas Television (RCTV), a private TV network and frequent government critic.
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The students do not have just one leader, but several, their ages ranging from 20 to 26 years. They appear regularly on television, have spoken before Congress and met behind closed doors at the nation's Supreme Court.
On Wednesday, hundreds of students clashed with police and the Venezuelan National Guard in Caracas, throwing stones as security forces responded with water cannons and tear gas.
Chavez has described his young-faced rivals as "daddy's little children", "fascists" and "the children of the rich," who he says are taking orders from U.S. government.
Many students brush such rhetoric aside.
"I feel sorry for a national government elected by seven million Venezuelans that has to lower itself to the level of a bunch of 20-year old kids to try to discredit us," said Douglas Barrios, a student leader from the private Metropolitan University.
But Chavez counts supporters among university ranks, too.
Some students who favor his constitutional overhaul said they are particular fans of one measure that would give students and university workers the power to choose school administrators by direct vote.
Chavez says that move will "take out the embedded elites who took over many of our universities."
Press; By FABIOLA SANCHEZ]
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