Chileans are heading to the polls to pick the country's next president and parliament, with former leader Michelle Bachelet widely expected to return to the presidency, three years after she left the post.
Bachelet had a substantial early lead in the first partial results on Sunday evening, winning 45.1 percent of the vote after 6.5 percent was counted, electoral officials said.
Her second-place rival Evelyn Matthei, the candidate for the right-wing governing coalition, had 24.8 percent, while seven other candidates had 11.9 percent or under.
A candidate needs 50 percent of the vote to win outright. If no-one crosses that threshold, the top two go through to a
run-off election on December 15.
Bachelet, 62, has promised to narrow the worst income inequality among the 34 member states of the Organization for Economic Co-Operation and Development (OECD) by leveling the playing field in education.
She has also pledged to rewrite a constitution that dates back to Augusto Pinochet's 17-year dictatorship, during which she was briefly a political prisoner. Her father, an Air Force Brigadier-General, was tortured and killed by Pinochet's regime.
Bachelet's centre-left Nueva Mayoria [New Majority] coalition, which spans the political spectrum from communists to moderate Christian Democrats, must also win big in congressional elections on Sunday in order to muster the political might needed to implement those changes.
"In order to confront inequality, I invite you to vote en masse for the Nueva Mayoria this Sunday. We want to win in the first round because we have a lot of work to do," Bachelet told a packed crowd at her campaign's closing ceremony on Thursday.
Trailing a distant second to the 62-year-old Bachelet in the polls is Evelyn Matthei, 60, the candidate for the governing right-wing Alianza coalition.
A candidate winning over half the votes would be elected outright - something that has not happened in 20 years. Otherwise, the two top contenders will go head to head on December 15.
One recent poll of likely voters suggested Bachelet may get the votes she needs for a first-round victory.
Other polls, however, have shown that support for the eight other candidates, including Matthei, maverick economist Franco Parisi and former socialist congressman Marco Enriquez-Ominami, could fracture the vote and push Bachelet into a second round against Matthei.
Bachelet, who held the presidency from 2006 to 2010, was constitutionally barred from seeking immediate re-election after her first term, but left office enjoying stratospheric popularity.
The Andean country moved to a voluntary voting system from a compulsory one last year, creating a degree of uncertainty in electoral forecasts.