By Sofia Menchu and Diego Oré
GUATEMALA CITY (Reuters) -Former first lady Sandra Torres was headed for an August run-off in Guatemala's presidential election after a vote on Sunday looked set to pit her against Bernardo Arevalo, another center-left candidate running on an anti-corruption platform.
The election, which has been dominated by concern over graft in the Central American country, is set for a decisive second round on Aug. 20 because Torres was falling far short of the 50% plus one vote needed for outright victory.
With returns counted from over three-quarters of polling stations, Torres of the center-left National Unity of Hope (UNE) had 14.9% of the vote, with Arevalo of Semilla, another left-of-center group, on 12.4%, preliminary results showed.
Torres told a press conference she was feeling optimistic. "We're happy," she said. "We're going to win, against whoever it may be."
But with nearly one in four ballots either spoiled or left blank, Guatemalans expressed discontent at the electoral process and the decision to bar early front-runner, businessman Carlos Pineda. Pineda urged supporters to spoil their ballots after he was ruled ineligible.
The third best-placed candidate, Manuel Conde, had 7.9%.
Opinion polls ahead of the election had not suggested that Arevalo, an ex-diplomat and son of former president Juan Jose Arevalo, would make the run-off. Arevalo has made tackling corruption a key priority of his bid.
"We didn't come to win the polls. We came to win the elections," Arevalo wrote on Twitter as results came in.
His party's previous presidential campaign was fronted by former attorney general and anti-corruption stalwart Thelma Aldana, though she was ultimately barred from running in 2019 on the grounds of alleged financial impropriety.
Aldana said the allegations were politically motivated due to the historic campaign against graft she waged together with the U.N.-backed International Commission Against Impunity in Guatemala (CICIG). The CICIG's mandate was terminated in 2019.
Aldana later sought asylum in the United States.
Stakes in the Guatemalan election are high, amid deteriorating standards of transparency and human rights in recent years, as well as poverty, corruption and violence.
Preliminary results pointed to a fragmented Congress, however, which could make it hard for the next president to govern.
Polls have suggested that the 67-year-old Torres will struggle to win a run-off given her unpopularity in the capital, Guatemala City, home to a high percentage of the electorate. She finished runner-up in the last two presidential elections.
The ex-wife of Alvaro Colom, Guatemala's president from 2008 to 2012, Torres was competing with over 20 other candidates, including Edmond Mulet, a career diplomat, and Zury Rios, daughter of the late right-wing dictator Efrain Rios Montt.
The race to succeed conservative President Alejandro Giammattei, who is limited by law to one term, was overshadowed by a court ruling blocking four candidates, including Pineda.
The United States and the European Union criticized the exclusion of Pineda, who called the decision "electoral fraud."
Meanwhile, unrest on Sunday in the town of San Jose del Golfo, near the capital, forced the postponement of voting there to August, the Supreme Electoral Tribunal said.
(Writing by Dave Graham; Editing by Stephen Eisenhammer and Toby Chopra)