A court blocked Colombian president Alvaro Uribe on Friday from running for re-election, making his former defence minister the favourite to succeed the Washington ally in a May presidential election.
The constitutional court ruling marked the start of a tough race to replace Uribe, who during his eight years in power became the country's most popular president for his US-backed war on leftist rebels and cocaine traffickers.
Juan Manuel Santos, a former Cabinet minister closely associated with Uribe's security success against Latin America's oldest insurgency, leads in opinion polls. After the ruling, he confirmed his intention to run for the presidency.
With Colombians waiting for word on their political future, the court voted 7-2 to reject a referendum on Uribe's re-election bid. It cited irregularities ranging from the referendum's financing to its rocky passage through Congress.
"I accept and I respect the decision of the constitutional court," Uribe said after the ruling. "One dream inspires me: that the country betters its path, but does not change it."
Under the conservative leader, the FARC or Revolutionary Armed Forces of Colombia, has been weakened, and foreign investment has flowed steadily into Colombia, an Andean country once a byword for a failed state mired in drug violence.
Many Colombians, even his foes, praised Uribe, the 57-year-old son of wealthy landowners, as a man who managed to steer the country onto the right track. But the re-election question dominated the political agenda for more than a year as Uribe remained evasive on whether he would run.
Any candidate to succeed Uribe is unlikely to shift far from his security policies, although most of the aspirants say they will seek to focus more on social development in the top coffee exporter and Latin America's No 4 oil producer.
"Uribe's sidelining from the presidential race is unequivocally positive in our view, opening the door to a deep bench of candidates who are broadly in favour of policy continuity," said analyst Patrick Esteruelas at Eurasia Group.
