A Colombian senator allied with President Alvaro Uribe has been targeted in a bomb attack in the capital, Bogota.
Senator Vargas survived a previous attack three years ago
German Vargas escaped unhurt, but nine people were injured when an explosion was set off as his car passed by.
Pedestrians and some of Mr Vargas' bodyguards were among the victims.
President Uribe condemned the attack and offered a $200,000 reward for information leading to the arrests of those responsible.
Mr Vargas was injured three years ago, when a package delivered to his office exploded.
At the time, Mr Uribe blamed the main left-wing guerrilla group, the FARC.
Mr Vargas is an outspoken backer of a proposal to let the Colombian president run for an unprecedented second term next year.
The senator has been mentioned as a possible candidate himself if Mr Uribe is barred by the courts from running in the May 2006 election.
Colombia's Constitutional Court is expected to rule in the coming days on a constitutional amendment passed by Congress last year that would allow Mr Uribe to seek a second term.
The latest opinion polls put the president substantially ahead of any possible rivals.