CARACAS (Reuters) - President Hugo Chavez needs to rely on a vast get-out-the-vote machine to avoid an unprecedented defeat when Venezuelans cast ballots on Sunday in a referendum on letting him run for re-election indefinitely.
Used to winning votes easily, the self-styled revolutionary trailed by a few points in most surveys over the past few days.
But pollsters say the narrow gap puts him in a statistical tie with the "No" camp and that his disciplined, state-backed political machinery could give him an advantage on vote day.
One survey on Wednesday by Consultores 30.11, which has worked for the government and accurately predicted a result last year, showed Chavez moving ahead -- by at least 7 points.
Buoyed by the OPEC nation's record oil prices, the leftist is a leading U.S. critic. Quick to hurl insults at foreign leaders, the Cuba and Iran ally also enters the vote in a diplomatic dispute with Colombia, Spain and the United States.
In office since 1999, Chavez wants a constitutional overhaul that includes permitting him to run again in 2012 and then to stay in power as long as he keeps winning elections.
Chavez is popular among the majority poor for funneling oil income into schools, clinics, and food subsidies.
Still, he faces the stiffest resistance to date among his own backers to his vision of a socialist state inspired by his mentor, Cuba's Fidel Castro.
Washington brands the leader of a failed 1992 coup as a destabilizing, anti-democratic force in Latin America, where his allies in Bolivia and Ecuador are also pushing left-wing reforms with constitutional rewrites.
He burnished his nationalist credentials on Wednesday by cutting diplomatic ties with Colombia after the collapse of mediation talks with rebels in the Andean neighbor.
His foreign minister also said Venezuela could expel a U.S. diplomat on suspicion of working against the reform.
Chavez, 53, says he needs a new mandate to extend his programs for the poor.
"The reform is essential ... to avoid the revolution losing its way, or pausing or worse still sinking," Chavez said.
He said he would prepare his suitcases, ready to leave office in 2013 should the reform fail.
If he wins, he promises 150 new laws.
Chavez used a mandate from a landslide re-election a year ago to nationalize swaths of the economy, shut the last nationwide opposition TV channel and rule by decree.
But longtime political allies have broken with Chavez over the new reform proposals, amplifying charges from a nascent student movement, religious leaders, traditional opposition parties and rights groups that the package is authoritarian.
Violence has marred the campaign, including the shooting death this week of a Chavez supporter. New York-based Human Rights Watch called for an impartial investigation into the campaign's clashes.
The changes would also allow Chavez to control currency reserves, censor the media in an emergency and pick party loyalists over regional elected officials.
He has sweetened the reform with proposals to shorten the workday and give pensions to street vendors and housewives. He says the package will empower community councils, which will receive funds to manage projects such as running gas stations.
Polls that show Chavez behind also say a majority of Venezuelans think he will win anyway. His vice president is a former head of the election authority, a body opposition supporters believe is loyal to Chavez.
Wall Street economists generally reckon Chavez will win but worry about political stability after the vote.
Chavez says the opposition wants to stoke clashes and will cry fraud if he wins and call backers onto the streets.
Chavez backers dominate the courts, Congress and the state oil company. On Caracas's state-operated subway, "Yes" campaign songs blare out at commuters.
For some voters, the government is trying too hard.
"If the reform were so good, they would not be doing so much campaigning," street vendor Maria Rubio said.