BOGOTA (Reuters) - Colombia's President Juan Manuel Santos kept his clear lead in voting intentions four weeks ahead of elections, although his closest rival, Oscar Ivan Zuluaga, continued to gain on the incumbent, a poll published late on Monday showed.
Center-right Santos would win 27 percent of the vote, according to pollster Cifras y Conceptos, up 4 points from its March survey. Right-wing Zuluaga, the anointed candidate of still-popular former President Alvaro Uribe, jumped 8 percentage points to 19 percent, the survey showed.
Santos would beat Zuluaga 34 percent to 31 percent in a second round of voting. The slim 3 point difference is a technical tie between the two candidates.
While all leading candidates appear to differ little on broad economic themes, a choice between Santos and Zuluaga for many voters is likely to come down to whose approach they prefer for ending a five-decade conflict with leftist guerrillas.
The negotiations with the Revolutionary Armed Forces of Colombia have made slow but promising progress since Santos initiated them 18 months ago. Zuluaga has said he would require the rebels to meet tougher conditions before continuing talks.
Like Zuluaga, Santos once gained support from the public backing of then out-going president Uribe, who decimated the guerrillas' ranks during his two terms in office with support from the United States. Santos' decision to engage with the FARC in peace talks has since turned the two into bitter rivals.
Support for Green Alliance candidate and former Bogota mayor Enrique Penalosa fell to 10 percent of voting intentions, down from 13 percent in March, tying with Clara Lopez of the left-wing Polo Democratico, whose backing jumped one percent.
Conservative Party candidate Marta Lucia Ramirez came last in the poll with 8 percent of voting intentions, although that was an increase from 5 percent in March.
The proportion of voters who plan to make a blank or protest vote, by choosing none of the candidates, fell 9 percentage points to 17 percent.
The survey of 2,500 respondents in 62 municipalities between April 26 and April 28 has a 2.9 percent margin of error.
(Reporting by Luis Jaime Acosta and Julia Symmes Cobb; Editing by Peter Murphy and Clarence Fernandez)