Tens of thousands of protesters marched in Caracas on Saturday to oppose a constitutional amendment that could allow President Hugo Chavez to run for re-election indefinitely.

Marchers waved the nation's flag and peered through glasses framed by the word "No" to encourage people to vote against ending term limits for all elected officials in a Feb. 15 referendum backed by Venezuela's socialist leader.

"Everything's gotten worse," said Yraiber Davila, a 24-year-old mechanical engineer who complained of rampant crime, a lack of government services and the difficulty of buying a house with annual inflation running at 31 percent in Caracas.

"I have a 10-year-old daughter and she's never seen another president," Davila said.

One protester carried a sign depicting Chavez as TV tough-guy Mr. T — complete with a Mohawk hairstyle and long, feathery earrings — beneath the phrase: "Indefinite Aggression."

Marchers chanted and wore emblems saying "No is no," a reference to a failed 2007 referendum that would have scrapped term limits and expanded Chavez's power. Chavez was first elected in 1998, and is barred under the current constitution from running again when his term expires in 2012.

Polls show Chavez gaining momentum before the vote.

Approval for the amendment stood at 51 percent in January — up from 38 percent a month earlier — the independent Venezuelan firm Datanalisis reported. The January poll of 1,300 likely voters had a margin of error of 2.5 percentage points.

Chavez's supporters say he needs to stay in power to oversee the completion of his socialist project, which they say has given the poor access to affordable food, education and health care.

But Ignacio Martinez, a 19-year-old economics student at the Metropolitan University in Caracas, said he believes allowing one person to stay in power for too long breeds corruption.

"A just and efficient democracy can't develop," he said.

While the march was largely peaceful, a group of four or five Chavez supporters attacked some straggling protesters as they began to march — punching them and burning their protest signs.

Chavez has spoken out against opposition-aligned student protesters for allegedly inciting violence — calling on authorities to disperse them with tear gas.

On Saturday, he also disowned groups of violent supporters, lamenting that they have enabled critics to accuse him of condoning violence.

He called on the Attorney General to detain Valentin Santana, leader of the pro-Chavez group "La Piedrita." A recently published interview with Santana quoted him as claiming responsibility for tear gas attacks and threatening to use arms against political opponents.

Police did not provide an estimate of the crowd's size, but protesters filled a major Caracas avenue and AP reporters at the scene estimated it to be in the tens of thousands.