Martelly's fledgling Reypons Peysan party won only three parliamentary seats and to enact the reforms Haiti needs so badly, he will have to forge deals with the ruling Unity Party, which consolidated its power in the legislature.
Diplomatic sources, meanwhile, claimed President Rene Preval's Unity used its influence to manipulate votes in the legislative elections in its favor.
"There was a lot of pressure" on election officials ahead of the official results unveiled earlier, a European diplomat said. "The international community is surprised by the difference between preliminary results and those unveiled yesterday."
Martelly, on a trip to Washington, urged his compatriots to work together.
"We shouldn't see this as an engagement into a fight between each other. We should see it as a collaboration, and this collaboration must be harmonious so it can be fructuous," he told journalists.
In Port-au-Prince, election officials confirmed the former singer and carnival entertainer's presidential victory -- with a resounding 67.57 percent of the vote -- over former first lady Mirlande Manigat.
Preval's Unity party expanded its presence in the lower house Chamber of Deputies, taking 46 of the 99 positions, and gained an absolute majority in the Senate with 17 of the 30 seats.
Martelly has yet to make an official announcement but observers believe he may ask Unity's Jean-Max Bellerive -- a respected figure well-known to the international community -- to stay on as prime minister and form a government.
|A man plays guitar in the earthquake destroyed Cathedral of Port-au Prince|
As Martelly courted vital foreign investment on his trip to the United States, violence erupted in several towns back home following the overnight announcement of the definitive poll results.
Demonstrators burned vehicles and blocked roads in protests linked to the legislative elections. At least one person was killed but UN police said the circumstances were unclear.
During his three-day trip to the United States, Martelly cut a very different figure from the bad boy entertainer of old and earned a ringing endorsement from US Secretary of State Hillary Clinton.
In addition to lunching with Clinton at the State Department, the incoming Haitian leader met with the chiefs of the Inter-American Development Bank, the World Bank, the International Monetary Fund and the US Chamber of Commerce.
"We were very pleased the financial institutions are open and flexible to new ideas and the interests of the people of Haiti. We are going to pursue them. Haitians do not want handouts. They want opportunities to create wealth," Martelly said.
"Haiti is open to the world, and we invite both tourism and businesses to come and visit as early as possible."
Already the poorest country in the Americas, Haiti was crippled by a January 2010 earthquake that killed more than 225,000 people, displaced 1.5 million, and left the capital in ruins.
The pace of reconstruction under Preval has been slow.
Martelly, who takes office May 14, has vowed his first six months will focus on moving hundreds of thousands of quake survivors out of squalid tent cities, tackling a resistant cholera epidemic and boosting agricultural production.
The international community has pledged billions of dollars to speed Haiti's recovery and former US president Bill Clinton, who co-chairs the reconstruction commission, has indicated funds will flow more freely once Martelly has a new government up and running.
"Once I am in office, my government will quickly do an overall assessment to ensure that foreign assistance is going to the people," Martelly said.
The problems are vast: from endemic poverty and corruption to reforming health and education departments largely dependent on foreign NGOs and dealing with a cholera epidemic that has claimed nearly 5,000 lives since October.
"Haiti today is the republic of NGOs," Martelly said. "The state has been weakened, and this must change. We need to build up the state's institutions while making the valuable work of the NGOs more effective and better for the needy."
Potential time bombs lie on the road ahead for Martelly in the shape of former dictator Jean-Claude "Baby Doc" Duvalier and Haiti's first democratically-elected president, Jean-Bertrand Aristide -- both recently returned to Haiti after years in exile.
Martelly backed away Thursday from earlier suggestions he would grant amnesties to the pair, saying that would be a matter for the judiciary.