(Adds figures for other candidates, election context)
BOGOTA, March 20 (Reuters) - Support for Colombia's center-right President Juan Manuel Santos has slipped in a survey of voters' intentions for May 25 elections, but he remains the clear front runner in a race that will center on how to end the country's five-decade conflict.
The Gallup poll published on the website of broadcaster Caracol showed Santos would gain 32.5 percent of votes, down 2 percentage points from the previous survey, and leaving him far short of the support needed to avoid a second round of voting.
Nonetheless, he retained a 17 percentage point lead over his nearest rival Oscar Ivan Zuluaga from the Centro Democratico party founded by ex-President Alvaro Uribe. Uribe has been a ferocious critic of Santos for engaging in peace talks with FARC rebels who have been fighting the government for five decades.
Zuluaga jumped 5 percentage points from the previous Gallup poll to 15.6 percent. If he and Santos proceed to a second round of voting, Santos would obtain 47.2 percent of votes versus 29.7 percent for Zuluaga.
Uribe's Centro Democratico, founded around more than a year ago, fielded candidates in congressional elections on March 9, garnering around 15 percent of the total vote for the Senate and just under 10 percent for the lower house.
That will thin Santos' congressional majority when the next legislature begins on July 20 and likely make it more difficult to pass new bills necessary to enshrine a future peace deal with the FARC in law.
On Wednesday, Santos ratified a decision by the country's inspector general removing the left-wing mayor of the capital city Bogota over mismanagement, a controversial decision which could cost him the support of some voters.
The survey put Enrique Penalosa of the Alianza Verde, or Green Alliance, in third place with 11.3 percent, followed by the Conservative party's Marta Lucia Ramirez with 9.3 percent. Clara Lopez of the left-wing Polo Democratico has the support of 8.6 percent of the electorate.
The survey of 1,200 people was carried out between March 13 and 17 in 60 towns and cities, and has a 3 percent margin of error. (Reporting by Luis Jaime Acosta; Writing by Peter Murphy; editing by Andrew Hay and Richard Chang)