Venezuelan President Hugo Chavez bade an emotional farewell to anxious supporters on Friday en route to Cuba for new cancer surgery, vowing to return for victory in the October election.

After a spirited speech on the steps of the Miraflores presidential palace, the socialist strongman rode through Caracas to the airport in an open-topped vehicle, raising his fist to cheering crowds.

Underlining the gravity of the moment, some Chavistas, as his supporters are known, shed a tear or raised hands in prayer.

I will fight for my life, said the 57-year-old president,

flanked by his weeping daughter Rosines.

Long live the Socialist Revolution! Long live Venezuela! Long live Chavez!

Chavez's trip to Cuba for surgery on a likely malignant lesion has given the lie to his previous claims of full recovery and thrown a wild card into the South American OPEC member's October 7 election that was already shaping up as a close race.

Chavez says he may need radiotherapy treatment after the operation scheduled for early next week in Havana - where he first had surgery for a cancerous pelvic tumour last year - raising the prospect of another lengthy convalescence.

But he has been upbeat in a stream of public appearances - citing uplifting texts from Jesus Christ to U.S. poet Walt Whitman and Venezuelan independence hero Simon Bolivar - about quickly conquering his latest health setback.

I dreamt a while ago of Christ who came and said, 'Chavez, rise, it is not time to die, it is time to live,' he said, alluding to the biblical story of Jesus raising Lazarus from the dead.

With cancer or without cancer, with rain, thunder or lightning, nothing and nobody can prevent the great victory of October 7. ... Soon we will return to the battle!

'NO SADNESS'

On Thursday night, Chavez sang and told anecdotes to raise the spirits of several thousand supporters in a Caracas theatre during a ceremony shown live, by government order, on all Venezuelan TV channels.

On Friday, also live on TV, he met with his Cabinet to give final instructions for government and signed a raft of deals with Chinese investors, before departing.

Despite the show of spirit by Chavez, some supporters and allies looked grave-faced and deeply moved.

Across the nation of 29 million people, Chavistas organized religious services and sent messages of support.

One group formed itself into a heart shape in coastal sand dunes that are a popular tourist spot in western Venezuela.

State TV dusted off images of a young Chavez rallying crowds, kissing children and playing sports.

We are the majority. There's no room for sadness, Chavez said. This was never in the plan for 2012, but those are God's ways.

Chavez's health woes have sent Venezuelan bonds higher on investor hopes for a more market-friendly government.

Opposition leader Henrique Capriles, the 39-year-old governor of Miranda state who admires the centre-left Brazilian government model, will face him in the October election.

While Chavez may benefit from a wave of sympathy, perceptions of physical weakness - particularly in contrast with Capriles' image of youth and energy - could offset that.

Before the announcement of his new surgery, opinion polls showed Venezuelans broadly divided, with a third pro-Chavez, a third pro-opposition, and a third undecided.

But the polls also gave Chavez a small edge in voter intentions - a fact analysts attribute to his popularity among the poor and an increase in welfare spending for the most needy.

SUCCESSOR?

Ruling Socialist Party members are under instructions not to discuss succession questions publicly. But media and political circles are rife with gossip over who, if anyone, might replace Chavez should he be incapacitated.

Dominating Venezuela since his first 1998 election win, Chavez has avoided grooming a successor.

None of the figures around him has his charisma, political and rhetorical skills, or connection with the masses.

In a paper titled The beginning of the end, Venezuela analyst Alejandro Grisanti of Barclays Capital said Capriles would be the winner if Chavez's health problems were prolonged.

If Chavez is out of the race, the chance for the opposition to win the election increases considerably, he said of the Democratic Unity coalition, which has united Venezuela's opposition groups after years of infighting.

Chavez has chosen Havana, over an offer from Brazil and some calls for him to show support for Venezuela's health system, because he is guaranteed discreet treatment by friendly authorities and reduced chances of media leaks.

He will also be able to enjoy the company of mentor and friend Fidel Castro, the former president of Cuba.

Venezuelan oncologist Sunil Daryanani said the fact Chavez's original tumour was found under an infection during his June 2011 treatment had made recurrence more likely because a wider area was affected.

Once they've opened him up, they'll have an idea if this is a localized occurrence - like a marble which they could remove totally - or something more advanced, he added.

I'm used to seeing patients deal with these sort of blows and they're normally very humble. Unfortunately, I think Chavez is also trying to draw political advantage from all of this.

(Additional reporting by Mario Naranjo, Deisy Buitrago and Girish Gupta; Editing by Peter Cooney)