Venezuelan president Hugo Chavez could win the right to be re-elected indefinitely if he wins a referendum to change the constitution.It is his second attempt to put an end to term limits after a similar vote was rejected in 2007. If he loses he will have to step down in 2013 when his current mandate ends. According to opinion polls, Chavez holds a slim lead although the outcome of the vote remains uncertain with many people still undecided ahead of the ballot. A close ally of Cuba’s Fidel Castro, Chavez claims he needs another 10 years to accomplish his vision of 21st century socialism in Venezuela. But detractors accuse him of trying to forge a communist dictatorship centred on his personal rule. Chavez also came under fire from critics for the expulsion earlier this week of a Spanish election observer, invited by the opposition, after he criticised a decision to keep polls open for two extra hours. Dozens of international monitors are present to oversee the fairness of the vote.