By Frank Jack Daniel

CARACAS, Feb 11 (Reuters) - Venezuela's larger-than-life President Hugo Chavez is playing for his future on Sunday in a referendum that may let him govern for another decade or more -- or end his socialist revolution in four years.

A high turnout is expected for the vote on changing the constitution to scrap term limits for the president and other politicians. Chavez has already been in office for 10 years but wants at least another decade to push through socialist reforms in the OPEC member country.

Popular for raising living standards during an oil boom, Chavez has a slim advantage in opinion polls but he could easily lose if turnout is low among his supporters or if undecided voters swing away from him.

A victory would encourage Chavez, who calls capitalism evil, to extend state control over the economy, give more farm land to the poor and hand power and money to loyal grass-roots groups even as Venezuela grapples with falling oil income that has already cost thousands of jobs in the oil sector.

This is Chavez's second attempt to change the rules so he can stay in power after he narrowly lost a first referendum vote in late 2007.

A new defeat would embolden the opposition and could be a turning point for the 54-year-old Chavez, who has led a growing bloc of leftist governments opposed to U.S. influence in Latin America.

Confident he will win, the ally of Cuba and Iran has in recent days taken a more conciliatory tone with opponents he usually describes as U.S. lackeys. He called the leader of a opposition group to wish him luck before a march, and also demanded the arrest of radical left-wingers who threatened and attacked an anti-government television station.

"We are the guarantee of peace, we are in the final week and I ask the people, state institutions, everybody to campaign in peace," he said at a campaign rally even as he vowed to "pulverize the 'No' vote."