SANTIAGO, Chile — Chile's president is asking his conservative bloc to pick a single presidential candidate and quickly overcome a political crisis just four months before the general election.

President Sebastian Pinera said Thursday that his Alliance coalition must be united and rapidly replace candidate Pablo Longueira. The former economy minister quit the race Wednesday to deal with his depression.

Longueira's resignation further weakened the chances that the conservative bloc will be able to beat former President Michelle Bachelet, the center-leftist who is the frontrunner in the Nov. 17 vote.

The current governing coalition led by the conservative Independent Democratic Union and the center-right National Renovation is the first conservative government since Chile's return to democracy in 1990.