But Rene Preval still may be able to govern effectively by reaching out to rival parties, observers say.
After the votes from Friday's elections were counted, the Lespwa Party won 11 of 27 Senate seats and 20 of 85 seats in the lower house or Chamber of Deputies.
Three Senate seats and 14 lower house seats are still open in areas where polling stations had to close due to violence or other problems. Those seats will be decided in another round of balloting at a later date, according to Reuters.
Preval, who was elected president Feb. 7 in the first election in the chaotic Caribbean nation since President Jean Bertrand-Aristide was pushed from power in February 2004 by a violent revolt, will be sworn in May 14.
Several other political parties expressed support for a Preval government. With their backing, Preval will have the 16-seat majority in the Senate but he still will need to reach out to other parties in the lower house.
"President Preval's administration can count upon our support in parliament," said Evans Paul, whose Democratic Alliance Party won one Senate seat and 11 in the lower house, Reuters reported.
"We are going to support the government of President Preval. There will be no obstructionism," agreed Micha Gaillard, a spokesman for the Fusion Social and Democratic Party.
"We have no interest in putting up opposition to President Preval," said Paul Denis, leader of the OPL Party. "He has shown openness, and all the conditions for governability are being met."