The coming referendum on turning Venezuela into the personal fiefdom of President Hugo Chavez may not be quote the sure thing that most experts were predicting just a few weeks ago.

Recent defections of long time Chavez supporters who oppose his plan to alter the constitution and place enormous power into the president's hands may have convinced many in the opposition to go to the polls and vote:

Few associates had been as loyal to President Hugo Chávez as the governor of the coastal state of Sucre, Ramón Martínez. And few are now more determined to defeat Chávez as he campaigns for constitutional changes that, if approved by voters on Sunday, could extend his presidency for life.

Chávez, 53 and in his ninth tumultuous year in office, was until recently predicted to win a referendum that would permit him to run for 8office indefinitely, appoint governors to federal districts he would create, and control the purse strings of one of the world's major oil-producing countries.

But Martínezand a handful of others who once were prominent pillars in the Chávez machine, have defected, saying approval of 69 constitutional changes would effectively turn Venezuela into a dictatorship run at the whim of one man. They have been derided by Chávez as traitors, but their unimpeachable leftist credentials have given momentum to a movement that pollsters say may deliver Chávez his first electoral defeat.

"The proposal would signify a coup d'etat," said Martínez, 58, whose dapper appearance belies his history as a guerrilla and Communist Party member. "Here the power is going to be concentrated in one person. That's very grave."

The biggest blow to Chávez came when retired Gen. Raúl Baduel, 52, turned against him this month. Chávez, Baduel and two other young army officers formed a clandestine anti-government group 25 years ago that eventually spawned the movement that ushered Chávez into power.

Later, as an army commander, Baduel remained loyal to Chávez during a brief 2002 coup that had tacit support from the Bush administration. Baduel said he remained loyal to Chávez because the coup was unconstitutional, and that he has now broken with the president for the same reason. He says a new constitution can be drafted by only an elected constituent assembly.