Colombians vote in test for Uribe allies

BOGOTA (Reuters) - Colombians voted in congressional elections on Sunday in a harbinger of May's ballot to replace President Alvaro Uribe, a U.S. ally who finishes two terms dominated by his war on leftist rebels.

Uribe's allies are seeking to build on their majorities in both houses of Congress and shore up his coalition, which threatens to break apart as member parties squabble over whether to present their own presidential candidates.

The conservative leader remains popular after taking the fight to FARC guerrillas and drug traffickers. Colombia's war has ebbed and foreign investment this year is seen increasing five-fold to $10 billion (6.6 billion pounds) since Uribe came to power in 2002.

A strong showing by Uribe's U Party will benefit Juan Manuel Santos, a former defence minister who is ahead in opinion polls and brands himself the successor to the campaign against the FARC or Revolutionary Armed Forces of Colombia.

But Santos still does not have the support to avoid a second round in June, and a weak result in Congress could convince other parties in the coalition to abandon a proposal for a unity candidate and launch their own presidential bids.

"For Sunday's election and for the May election, we share the same objective, to defend, continue, and improve on the legacy of President Uribe," Santos told a party assembly before the legislative vote.

The election race has heated up since February when a court ruled Uribe could not run for a third consecutive term. Any candidate to replace him likely will adhere closely to his popular security and pro-investment policies.

Voters will elect 102 senators and 166 representatives on Sunday. Candidates range from veteran party chieftains and former hostages of FARC rebels to soap opera celebrities and national soccer players.

Uribe's alliance, made up of his U Party, the Conservative Party, Cambio Radical Party and a group of smaller parties, holds a majority of 68 seats in the Senate and a 107-seat majority in the lower house.

BATTLE IN THE ALLIANCE

But Cambio Radical has shifted away from the government alliance and its own candidate, veteran lawmaker German Vargas Lleras, is already campaigning.

The Conservative Party -- a key alliance member -- also holds its internal election to decide a presidential candidate, which could result in a splinter for the coalition if the winner decides to face Santos rather than support him.

"Today's elections will give a clearer panorama of the strength of the groups in the running for May 30," the newspaper El Tiempo said in an editorial. "One race finishes today but another begins."

Rebels usually step up attacks during elections. Police uncovered two bomb plots on Saturday. Authorities halted several attacks on Sunday and reported heavy fighting with rebels in southern Cauca province. But voting went ahead peacefully across the country.

The next government will need a majority in Congress to push through health reforms, alongside changes to the pension and tax systems and rigid financial transfers to regional administrations -- all important for tackling the deficit.

Sunday's vote will also test how influential Colombia's armed groups remain in politics.

During Uribe's second term, the Congress was caught up in a scandal tying dozens of lawmakers to paramilitaries who smuggled drugs and massacred peasants in the name of counter-insurgency before disarming under his government.

Violence and kidnapping from the war has dropped sharply but a report by the national ombudsman said illegal armed groups are still a risk to voting in a third of Colombia's more than 1,000 municipalities.

(Editing by Cynthia Osterman)