By Helen Murphy and Luis Jaime Acosta
MARQUETALIA, Colombia, May 20 (Reuters) - From shallow trenches carved into an isolated mountain range, Manuel "Sureshot" Marulanda led a long battle against thousands of U.S.-backed troops seeking to wrest control of the area from his small band of peasant fighters.
The ground and air onslaught lasted four months but Marulanda and his 47 combatants survived it, finally escaped through the tree-covered mountains of Marquetalia and went on to form the Revolutionary Armed Forces of Colombia (FARC).
Five decades after the battle that launched its communist insurgency, Latin America's longest-running rebel group is now negotiating a peace deal to end a war that has killed over 200,000 people and then seek power at the ballot box.
Critics say the FARC's Marxist rhetoric is too entrenched to attract popular support, but sympathizers say its leaders are shrewder than given credit for and could morph into a leftist movement with electoral appeal.
"Democratically, that's the key word," said coffee farmer Oswaldo Vanegas as he bought unrefined sugar in Gaitania, a hamlet close to Marquetalia, the FARC's birthplace, in central Colombia. "If people like the FARC's message then it will be successful. If not, it will fail. We need to hear the message."
President Juan Manuel Santos, who launched the peace talks in late 2012, is encouraging the FARC to enter politics but believes it is way too radical to end Colombia's traditional conservative sway.
"I don't think the Colombian people would be convinced by its thesis because it's obsolete, it's out-of-date communism," Santos told Reuters while campaigning for a second term in the presidential election on Sunday.
"If it evolves, becomes a more moderate, rational left then it will have more space. But if it maintains its orthodox, fundamentalist, Marxist-Leninist position it won't obtain much politically."
The two sides at the peace talks, held in Cuba, have already clinched partial deals on the rebels' participation in politics, agricultural reform and ending the drugs trade.
They have not given details but rebel leader Ivan Marquez said the FARC, which celebrates its 50th anniversary next week, is "completely satisfied" with the proposed move into politics, calling it an important step toward real democracy.
"The destiny of the nation depends on the participation of all its citizens and not a handful of privileged oligarchs to squander and plunder," he said.
The presidential election is seen as a referendum on the peace talks, the most serious effort in years to end a conflict that forced millions to flee their homes and helped Colombia's cocaine trade flourish.
After surviving the army offensive at Marquetalia in 1964, the FARC spread to rural areas across Colombia. Funded by extortion and cocaine, it grew to a fighting force of 20,000 in 1999, when it reached the mountains above the capital, Bogota, and threatened to seize power.
But it was then weakened as the U.S. government poured billions of dollars into Colombia's anti-insurgency campaign. The FARC now has around 8,000 fighters.
Some old friends of Marulanda - who continued fighting from the jungles until his death of a heart attack at aged 77 - say they hardly recognize the FARC of today, corrupted by the drugs trade and by decades of violence.
Sitting under a tree in Gaitania, hours from Marquetalia on horseback along a mountain precipice, Humberto Tafur recalls Marulanda as a brilliant, disciplined man who trusted no one.
"He was friendly, very formal, but also very malicious and restless," said Tafur, 71, whose mother would cook for Marulanda when he came to town. "The problem is that his FARC family got too big and lost its way. It's a very different group now.
"It should get its ideas heard in Congress though because from that will grow new ideologies. It has some good ideas."
RISKY MOVE INTO POLITICS
Other Latin American guerrilla groups have given up their weapons and joined electoral politics, with mixed results.
El Salvador's Farabundo Marti National Liberation Front (FMLN) became the main opposition party after signing peace in 1992 and 17 years later won the presidency. It recently won a second term in power.
In contrast, Guatemala's leftist rebel group has been unable to gain any traction in politics since it gave up arms in 1996.
Colombia's M-19 declared peace in 1990 and former fighters won office as they eased their Marxist rhetoric and policies, including the current mayor of Bogota, but the group is still a long way from winning the presidency.
Although FARC leaders favor the rhetoric of revolution, scholars say they have already started to ease their political stance and tailor it to a more modern Colombia.
"The FARC is more realistic now to changes in Colombia and worldwide. It knows its Marxism doesn't inspire the youth as before, so its message changed," said Mario Aguilera, author of a book on the FARC.
While they want peace, many Colombians are appalled by the idea of rebel leaders joining politics, and staying out of jail.
Oscar Ivan Zuluaga, a right-wing candidate backed by former President Alvaro Uribe, is fiercely critical of peace talks and says rebel chiefs should be barred from politics.
Zuluaga is expected to force Santos into a run-off vote next month. If he wins, it could throw the peace process into doubt.
Government and rebel negotiators are still trying to reach agreement on two other key issues, reparations for war victims and the mechanics of ending the conflict.
The FARC is able to attack military targets and damage Colombia's mining and oil industries but after more than a decade of reversals it is no longer a threat to state power.
As its long war may be drawing to an end, elderly residents here recall how Marulanda, who won his nickname "Sureshot" for killing a policeman in Gaitania's square from the mountains above, began as a supportive leader who later turned on them.
"At the start, he would ensure that children were fed," said Rogelio Orozco, 75. "The farmers had respect for them. Then they attacked us, they killed my brother," he said lowering his voice and glancing around. "I don't think they will ever change their ideology."
Only 16 families still live in Marquetalia, mostly milk and bean farmers.
"This is an area made famous by the FARC, a terrorist area, the rebels' birthplace, but now it's just us farmers trying to make a living and we are totally abandoned," Hector Maldonado, 29, said of the area that once cultivated poppies for heroin production. "We have no roads, no electricity, no dignified homes, nothing. We have been forgotten." (Additional reporting by Julia Symmes Cobb in Bogota; Editing by Kieran Murray)