A charismatic businessman seen by Chile's centre-right government as its best hope for holding onto power has been forced out of the race by a financial scandal.
Former public works minister Laurence Golborne is widely known for supervising the rescue of 33 miners trapped far underground in the Atacama Desert in 2010.
But he is also a former chief executive officer of retailer Cencosud, and his candidacy suffered a severe blow last week when the Supreme Court fined the company 70 million US dollars (£45 million) for increasing its supermarket unit's credit card maintenance fees when he was in charge in 2006. The court said card clauses were abusive and affected 608,000 clients.
Mr Golborne's candidacy was also troubled by accusations that he did not include information about an offshore account registered in the British Virgin Islands in his declaration of assets.
"I want to be clear: I don't want to be an obstacle to any decision," Mr Golborne said. "As of this moment I bring down my candidacy in all forms for this nomination. Decide freely what is best for the country."
The resignation is expected to weaken the possibility that a candidate from the conservative governing coalition can beat former president Michelle Bachelet, the socialist who is the front-runner in polls for the November 17 election.
"This leaves the Alliance in a situation with diminished real opportunities of challenging Michelle Bachelet, who has been consolidating as a real alternative," said Guillermo Holzmann, political science professor at the Universidad de Valparaiso.
Mr Golborne had been competing against former defence minister Andres Allamand for a chance to represent the centre-right coalition in the primary election to be held on June 30.
Economy minister Pablo Longueira announced late on Monday that he would join the race. "I want to sincerely tell you that this the biggest sacrifice I've ever made and that I won't give up because I know the country needs us to go out and reach every corner of Chile more than ever," Mr Longueira said. "Chile is the first country in Latin America that has a real chance to reach development. It can become a country where there's less poverty and less inequality."
Chile, the world's biggest producer of copper, is respected for its fast-growing economy, solid institutions and low unemployment rate. But it also has the worst inequality rate among the 34 countries of the Organisation for Economic Co-operation and Development. The next president will have to tackle mounting social demands and frequent protests demanding a wider distribution of Chile's copper wealth, the preservation of the environment and free education.