The Central Election Commission's preliminary results indicate Mirlande Manigat, whose husband was ousted by the country's now-disbanded military in 1988, led balloting in the Nov. 28 election, followed by Jude Celestin, whom Preval selected as his successor, CNN reported Wednesday.
The third-place finisher, musician Michel Martelly, who just missed the Jan. 16 runoff, challenged the results, alleging fraud.
"The math says an absolute fraud," said Damian Merlo, Martelly's campaign manager.
Preliminary results indicated Manigat received 31.37 percent of the vote, followed by Celestin getting 22.48 percent, and Martelly capturing 21.84 percent.
Gunfire resounded and demonstrators set tires on fire Tuesday after election officials announced preliminary results, The Miami Herald reported.
Nineteen candidates sought to succeed Preval, barred from seeking another term, who has become increasingly unpopular as Haiti is still trying to recover from a devastating earthquake in January and is in the grip of a cholera epidemic.
Candidates have 72 hours to challenge the preliminary results, the Herald said.
"These elections need to be annulled. The next step, we meet ... to watch what the reaction is throughout the country," said candidate Charles-Henri Baker, who finished sixth with 2.38 percent of the vote.