BOGOTA (Reuters) - Colombian President Juan Manuel Santos' popularity rose for a third straight month in December and he would be re-elected next year in a second-round vote, a poll published on Thursday showed.
Santos' approval increased to 45.1 percent from 36.9 percent in November, according to the first Gallup poll since announcing he would run for re-election next year.
The center-right president would win 38.5 percent of the vote if a first-round election scheduled for May took place now, up from 27 percent a month ago. The poll said Santos would take 47.5 percent in a second ballot and win the presidency.
A candidate needs more than 50 percent to win the presidency in the first round, while the second round goes to the candidate with the most votes.
Santos would beat opposition candidate Oscar Ivan Zuluaga, who represents former President Alvaro Uribe's new political party, by a wide margin in both rounds. Zuluaga would receive 13.6 percent support in May voting and 23.9 percent in June, according to the poll, which was conducted between December 2 and 9.
"Santos' decision to seek reelection, the advances in peace negotiations, a decent economic performance and backing from the United States have all contributed to an improvement in his favorable image and voter intention," said Jorge Londono, head of Gallup Colombia.
Santos' approval has improved in the past months from a record low as government peace talks with Marxist FARC rebels showed signs of progress. Last month the two sides reached agreement on the rebels' participation in the political system, the second and possibly toughest item on a five-point peace agenda.
Santos took office in 2010 with an approval rating of 74 percent and maintained decent ratings through the beginning of peace talks with the Revolutionary Armed Forces of Colombia, or FARC. But the initial euphoria soon wore off as Colombians judged the year-long negotiations had yielded little.
The new poll showed an improvement in Santos' popularity for a third month. In September his support slumped to a record low after a two-week farmers' strike was broadcast on television with images of riot police wearing armor confronting workers dressed in ponchos.
As many as 28.1 percent of Colombians would cast blank votes in the first round, the December poll showed, an indication that they are not satisfied with Santos and do not yet know much about the alternative candidates. The blank vote last month was 30.6 percent.
Gallup spoke to 1,200 people in more than 50 cities and towns across Colombia. The survey had a margin of error of 3 percentage points.
(Reporting by Helen Murphy and Luis Jaime Acosta Editing by W Simon)