Former President Michelle Bachelet, who retained huge approval ratings even after yielding to Pinera in 2010, has announced she will run for a new term in office in the November election.
Pinera cannot seek re-election but his Coalition for Change, which includes National Renewal and Independent Democratic Union parties, is fighting to retain power in the Nov. 17 election.
Pinera, a millionaire, rose to power with the pledge to put all of Chile into the 21st century with sweeping economic and social reforms. His plan was interrupted by a magnitude 8.8 earthquake that required massive investment in reconstruction. But Pinera was also faulted for lack of communications skills that wiped off his approval ratings.
Pinera's presidency has been marked by violent student protests over the government's failure to reform an education system that favors the country's wealthy minority and burdens less privileged middle and working class pupils with financial liabilities beyond their means.
Pinera has also faced criticism for ignoring environmental concerns and interests of native Chilean communities while pushing for multibillion-dollar projects backed by private business.
This week's legislation announced a special bonus payment of $85 for low-income families that could cost the treasury $208 million.
Critics say the handout won't narrow the poverty gap that puts at least 15 percent of Chile's population of 17.2 million among the most deprived and underprivileged in the country.
Handout payments are to start April 8 and are aimed at easing financial burden for impoverished families with school-going children. Pinera's opposition critics say the measure isn't enough even to cover the essentials for school-goers including registration fees, school books and uniforms.
Opposition critics want economic and fiscal reforms that reflect a more equitable distribution of the country's annual per capita income of $18,400. More than 15 percent of Chileans subsist on $2 a day.
Bachelet recently gave up her job as the head of the U.N. Conference on the Status of Women to run for president.
"I told you before that we would talk [about my candidacy] in March," she told a gathering at a photography exhibition devoted to her term as president. "And here I am, ready to fulfill this challenge. I have made the decision to be a candidate."
A recent poll found Bachelet 28 points ahead of her closest rival for the presidency, conservative former Mining Minister Laurence Golborne, who gained popularity managing the 2010 rescue of 33 miners in Copiapo, Atacama Desert.
Pinera is prohibited by Chile's Constitution from seeking a second consecutive term, as Bachelet was in 2010.
The U.S. ambassador to the United Nations, Susan Rice called Bachelet's departure "a major bummer."
"She is awesome and helped save #CSW 2013," Rice added in a Twitter posting, in a reference to the U.N. body.
U.N. Secretary-General Ban Ki-moon said Bachelet helped win major advances for women and promised she "will always have a home at the United Nations."
Bachelet, a doctor, became Chile's first female president in 2006 after serving as defense and health minister.
Chilean women's plight increased under the dictatorship of Augusto Pinochet and deep-seated male prejudice against equality for women remains entrenched, a U.N. study said.
A 2010 U.N. Development Program report said 62 percent of Chileans opposed full gender equality. A follow-up 2012 World Development Report reflected some positive change. Chilean male attitudes showed "men do not lose out when women's rights are promoted," said the study.