Wickremesinghe faces two formidable opponents. One is Anura Kumara Dissanayake, the leader of a once-marginal Marxist party tarnished by its violent past.
The party led two failed uprisings in the 1970s and 1980s that left more than 80,000 dead, and it won less than 4% of the vote in previous parliamentary elections.
But the crisis in Sri Lanka has proven an opportunity for Dissanayaka, 55, who has enjoyed a surge in support thanks to his promise to change the island’s “corrupt” political culture.
He told a polling station that he was confident of winning the top job.
“After the victory, there must be no more clashes, no more violence,” he said. “Our country needs a new political culture.”
His opposition counterpart, Sajith Premadasa, 57, the son of a former president assassinated in 1993 during the country’s decades-long civil war, is also expected to perform well.
Premadasa has pledged to tackle endemic corruption, and he and Dissanayaka have pledged to renegotiate the terms of the IMF bailout.
