Factbox: Colombian candidate Santos

(Reuters) - Colombia's former defense minister Juan Manuel Santos is ahead in polls to succeed President Alvaro Uribe, who was barred from seeking re-election in a May 30 vote.

But he faces a tough race, and a possible second round in June, as rivals jockey for position now that Uribe has been taken out of the race.

Here are some facts about ex-minister Santos:

* Born into a wealthy Bogota family who once owned the El Tiempo newspaper, 58-year-old Santos was a cadet at a Colombian naval academy before studying economics, public administration and journalism at universities in the United States and the United Kingdom. He was for a while a newspaper columnist and won a Spanish prize for a series about the Sandinista movement in Nicaragua. His family has long been involved in national politics and his cousin is vice president of Colombia. He is married with two sons and a daughter.

* Meticulous about his appearance, Santos is known as an astute political operator and heads Uribe's national party. But he has been criticized for lacking the popular touch Uribe demonstrated with poorer voters. He is an experienced bureaucrat having held an array of government offices. He started in the country's coffee federation and later held defense, trade and finance minister posts. Santos was praised for his deft handling of the country's fiscal crisis during his time at the finance ministry under then President Andres Pastrana.

* His most successful government position was as Uribe's defense minister and as the architect of some of the most successful strikes against the leftist rebels from the FARC, or Revolutionary Armed Forces of Colombia. During 2008, flanked by the top military brass, he was the public face that announced the deaths or surrender of several top FARC commanders. When the military managed a spectacular rescue of a group of rebel hostages, including French-Colombian politician Ingrid Betancourt, Santos burnished his credentials by appearing with her as she stepped off a plane at a Bogota airport after years in captivity. But his term as minister was also marred by a scandal over troops who helped murder civilians to count them as rebels and inflate their success rate in combat.

* Ties with Colombia's leftist Andean neighbors have soured under Uribe, and Santos, as defense minister, became the target for Venezuelan President Hugo Chavez and Ecuador's President Rafael Correa. Ecuador tried to have him extradited to face charges for a raid into Ecuadorean territory to kill a Colombian rebel hiding over the border. Chavez branded Santos part of a Colombian right-wing elite working against his socialist government. He called Santos "a threat to peace in South America" and promised he would deploy his Russian-made Sukhoi jets if Colombia's military moved against him. Santos says he and Chavez are like "oil and water" but says he could work with the Venezuela if there were mutual respect.