Chile has prospered under Pinera but, at the same time, been saddled with political turmoil over the country's top-heavy social structure, where analysts say a tiny elite holds sway and perpetuates chronic inequality in education, income distribution and discriminatory class structure.
Entrenched wealthy elites so far have thwarted efforts by Pinera to dismantle those structures, reform the class-driven education system and blunt economic instruments that hold back Chileans on low wages. Millionaire Pinera has faced charges, which he denies, that he's a member of the elite: uncaring, aloof and unaware of the pain of the poor.
In contrast, Bachelet, 62, left the presidency in 2010, her popularity intact, after a four-year term as the constitution required. She now leads the polls before the first round of presidential election Nov. 17.
Analysts say Bachelet needs to win a clear majority to support her promised reforms, often described in the media as a kind of palace revolution. If elected, Bachelet wants to tax the rich, raise corporate taxes and rewrite a constitution inherited from the 1973-90 dictatorial regime of Augusto Pinochet.
Support for such sweeping reforms is far from guaranteed, analysts say. While most of her proposed changes will win her popularity, Bachelet will struggle to get such radical reforms through congress, challenging legislators with entrenched ties in the system she wants to reform.
Chile's high-income economy has won the country membership in the Organization of Economic Cooperation and Development group of industrial nations, and praise from the United Nations and the World Bank. But Chile has also drawn criticism because of the level of economic inequality measured by the Gini index.
Bachelet has alarmed Chile's economic elite with promises of widespread change. An estimated 47 percent of Chileans surveyed for a poll said they would vote for Bachelet while only 14 percent backed right-wing candidate Evelyn Matthei, 59, and 10 percent supported independent economist Franco Parisi. About 16 percent were undecided or unlikely to vote.
Matthei's approval ratings got hit by family associations with the Pinochet regime and public disenchantment with the right-wing coalition she represents, which also backs Pinera.
Analysts said Bachelet's chances of securing a comfortable majority in the Legislature to carry through her radical reforms could still be affected by skepticism about the outcome of proposed changes and their likely impact on both the rich and the middle class. Bachelet's taxation reforms in particular have put many entrenched vested interests on guard.
Bachelet is back as a presidential candidate because Chile's electoral law allows non-consecutive re-election. Election is direct by an absolute majority. If no candidate obtains such majority, a runoff election determines the winner between the top two vote-getters.
Foreigners legally resident for five years or more also are allowed to vote.