* Uribe's favorite enjoys late surge in polls
* Spy scandal may hurt Zuluaga in final days
By Helen Murphy
BOGOTA, May 19 (Reuters) - Since stepping down as Colombia's president, Alvaro Uribe has spent much of the last four years fuming as his hand-picked successor turned against him and began peace talks with Marxist guerrillas.
Now Uribe is throwing his support behind right-wing economist Oscar Ivan Zuluaga and a late surge in opinion polls has raised his hopes of ousting President Juan Manuel Santos from power.
Zuluaga is the candidate of a new opposition movement that Uribe founded last year and he is staunchly against talks with rebels of the Revolutionary Armed Forces of Colombia (FARC).
Like his hardline mentor, Zuluaga accuses Santos of selling out Colombians by promising congressional seats instead of prison cells to rebel leaders if they end the 50-year-old conflict that has killed more than 200,000 people.
Opinion polls ahead of the first round of voting on Sunday show Zuluaga catching or even overtaking Santos, although a widening scandal over the alleged hacking of rebel negotiators' emails by Zuluaga's campaign could hurt him.
Neither man is expected to win the 50 percent support needed for a first-round victory, meaning they would go into a run-off on June 15.
A victory for Zuluaga could mean the end of peace talks and an escalation of U.S.-backed bombing campaigns that were central to Uribe's counter-insurgency strategy when he was president.
"One of the most important tasks for the next president is to guarantee the security we had between 2002 and 2010 and so ensure true peace for Colombia," the 55-year old Zuluaga says in campaign ads.
Unseating Santos would also be a huge personal victory for Uribe, who has not forgiven him for his perceived "betrayal".
In angry Twitter posts, he regularly accuses Santos of using him to get into office in 2010 by promising to continue Uribe's hardline policies only to secretly prepare peace talks.
"It's painful. We are parents and grandparents, it hurts that Santos's government prefers electoral deals with murderers," Uribe said recently about talks with the FARC.
"President Santos, is this what why you were elected four years ago?" he said in another.
Elected to the Senate in March, Uribe's populist appeal has helped revitalize Zuluaga's lackluster campaign.
Once widely seen as staid and boring, the former finance minister with bushy eyebrows now appears to have overcome his reputation as an insipid technocrat.
TV spots show him pumping his fist as he punches out policy ideas at packed rallies, receiving admiring stares from giddy teenagers, and taking swipes at Santos.
Swapping pin-striped suits for blue jeans and cowboy hat, Zuluaga has traveled the nation - often with Uribe - to meet coffee farmers in Pereira, coca growers in Putumayo and ranchers in Cordoba.
But many Colombians wonder if he would move out from Uribe's shadow or instead allow him to govern behind the scenes.
"Everyone knows Uribe wears the pants in that relationship," said Alirio Sanchez 46, a laborer on fruit plantations outside Bogota. "But Zuluaga seems to have some good ideas."
NO LOVE LOST
Security improved significantly under Uribe although his fierce campaign against the FARC often seemed to border on the personal: his father was killed by the rebels in a botched kidnapping. Some believe he will only be content if the rebels are crushed on the battlefield.
Uribe left office with high approval ratings and he remains popular but his legacy was tainted by accusations of corruption and of wire tapping opposition politicians and journalists.
A similar scandal is now hurting Zuluaga.
Colombia's chief prosecutor alleges that Zuluaga's camp sought to damage the peace talks by hacking into negotiators' emails - and Santos's - and the scandal could harm Zuluaga in the final days of the campaign.
A video appears to show Zuluaga being briefed about secret military intelligence by a man now in custody and facing spying charges for his role in the hacking case. Zuluaga had denied knowing what the alleged hacker was doing and how any data could be used in his campaign.
He said the video is a montage but some of his rivals called on him to pull out of the race.
Still, Zuluaga and Uribe appeal to Colombians who are skeptical of the peace talks.
During negotiations in the late 1990s, the FARC was ceded a Switzerland-sized area to run and used it to strengthen its military position while continuing to kidnap people and use the cocaine trade to fund the conflict.
Zuluaga says if elected he would give the rebels eight days to down their weapons and halt talks if they refuse.
The FARC has refused a unilateral ceasefire.
While Santos is campaigning on the issue of peace, Zuluaga has coupled criticism of the talks with a focus on fighting crime, improving health and education and creating jobs.
Polls show those concerns are more weighty than war which is no longer a daily worry for many, particularly in urban areas.
Still, Santos pulled out an ace card last week with government and rebel negotiators reaching a deal on the third item of the five-point peace agenda: the illegal drugs trade.
If Santos can turn that advance into votes, Uribe's hopes of putting another ally in office may be on hold for at least another four years. (Additional reporting by Julia Symmes Cobb; Editing by Brian Ellsworth and Kieran Murray)