Tens of thousands of Venezuelans streamed through the streets of Caracas on Saturday to protest leftist President Hugo Chavez's second attempt to change the constitution to let him govern as long as he wins elections, according to Reuters. Opinion polls give a slight lead to Chavez ahead of a Feb. 15 vote on whether to allow the president and other politicians to run for re-election as many times as they like in South America's top oil exporter. In 2007, voters rejected a similar proposal. The march, under the slogan "no is no" and led by anti-government students and political parties who claim Chavez will turn Venezuela into a version of communist Cuba, was the largest by the opposition in more than a year. "This reform hides, as President Chavez himself has said, the start of what would be a country, a state with a Castro-communist system," said Manuel Rosales, a former opposition presidential candidate. Chavez, a vocal critic of the United States, is close friends with former Cuban leader Fidel Castro. Organizers of the march said hundreds of thousands of people took part, while government television said turnout was low. Protesters complained about a large rise in violent crime under Chavez and wore shirts emblazoned with the phrase "I also want to be president." Many carried Venezuela's red, yellow and blue flag in the march that stretched from the edge of the city's largest slum into a wealthy business district. Street vendors sold gas masks to protesters fearing a repeat of clashes with the police that have plagued smaller opposition marches in recent weeks. Chavez has nationalized industries and raised spending on health and welfare since he took office in 1999 but says he needs more time to build what he calls "21st Century socialism" in one of the principal oil suppliers to the United States. Still popular with about half of the population, he has amassed a great deal of power and most institutions are run by his allies. Opponents say Chavez is authoritarian and will turn people's homes and possessions over to the state. Venezuela has close ties to Cuba, which provides thousands of doctors and security officials in return for cheap oil, but Chavez denies he will prohibit private property and points out the government still works with foreign oil companies. Chavez has won multiple elections in the last decade and survived a brief coup, a months-long shutdown of the vital oil industry and a recall referendum. Despite large street marches, the opposition only recently made gains against Chavez, defeating the 2007 referendum and winning key seats in state and city elections last year. Apparently confident of victory, Chavez has toned down his usually aggressive rhetoric against the opposition in recent days and on Friday said he welcomed the opposition march. If he loses, Chavez should leave office in four years, although he does not rule out trying again to change the electoral law. In comparison to the violence that often accompanies Venezuelan politics and despite a spate of scuffles between police and student protesters, campaigning from both sides has mainly been low key this year. With only a small lead in polls before the referendum and fearful of a repeat of his 2007 defeat when millions of his supporters chose not to vote, Chavez is pushing for heavy turnout by his backers at polling stations on Feb. 15.