Fernando Lugo, who was swept to power in Sunday's election by promising to help the poor and indigenous, has also pledged to try to clean up the practices that have given Paraguay the reputation for being one of the most corrupt countries in South America and a haven for smuggling.
The gray-bearded former bishop, whose five-year term begins Aug. 15, embarks on a transition from one political party to another not seen here since the Colorado Party began its reign in 1947, before the communist parties in Cuba, China and North Korea took power.
The challenges he faces are tough: double-digit poverty, high illiteracy, 300,000 landless peasant farmers clamoring for help and the notorious corruption spawned by a huge informal economy in contraband goods.
Riordan Roett, head of Western Hemisphere studies at SAIS-Johns Hopkins University, said Lugo will have scarce wiggle room.
"The economic realities give the new team very little room to maneuver," he said, with plenty room for a fall. "Good luck Bishop ... or you may find yourself in exile pronto."
When word of Lugo's election victory over Colorado Party candidate Blanca Ovelar emerged late Sunday, tens of thousands of his supporters took to the streets in gleeful celebrations. But good will could be short lived.
"My dad is a construction worker but he's out of work because people don't have money to build anything," said Maria Ines Gonzalez, waving a flag of the opposition Liberals who are part of Lugo's left-of-center coalition. "Lugo is a priest who understands the needs of the poor and I believe he is going to solve many social problems."
Other Paraguayans are adopting a wait-and-see approach.
"Lugo made a lot of promises and we're tired of promises. We'll have to wait at least a year to see if he does anything, especially if he can give work to young people," said Rodney Bernal, a hotel security guard who watched horn-honking opposition celebrations.
The triumph of Lugo's eclectic opposition alliance heralded the latest in a series of electoral wins by leftist, or center-left, leaders in South America.
Yet he is an untested newcomer to politics who forged his anti-Colorado coalition just months ago.
"You have decided to be a free Paraguay," Lugo told cheering supporters as he thanked them for shucking off 61 years of uninterrupted Colorado Party rule.
But he must still overcome the deep presence of the Colorado Party in many aspects of society.
"This is a crazy country, full of corruption," said 56-year-old Irene Villalba, who complained the Colorados had infiltrated all corridors of power and accumulated power through its state apparatus.
Lugo must also deal with the legacy of the virulently right-wing dictatorship led by the late Gen. Alfredo Stroessner, which lasted until his ouster in 1989.
The Colorado Party emerged from a 1947 civil war to begin its long rule in Paraguay. When Stroessner seized power in 1954, he recruited the party as an acquiescent "twin pillar" alongside his repressive military in ruthlessly holding power.
Through public works projects and patronage doled out by the Colorado's vast state apparatus, Stroessner oversaw Paraguay's transformation from open sewers and no running water even in the capital to a more modern nation.
In turn the Colorado party, the only one allowed by Stroessner, let him arrange to be elected every five years. Under the dictatorship all military personnel and civil servants, including teachers, were required to be loyal card-carrying party members. Purges were common, with paid informants often denouncing anyone suspected of disagreeing with Stroessner.
After Stroessner's ouster, free elections led to a succession of Colorado presidents despite sporadic political unrest and party infighting. But countless corruption scandals blamed on elites within the party beginning in the late 1990s engendered new dissatisfaction with a party that still controlled a vast bureaucracy, jobs and also was accused of disrupting Paraguay's judicial independence.
It was only eight months ago that Lugo welded leftist unions, Indians and poor farmers into a coalition with Paraguay's main opposition party: the conservative Authentic Radical Party. He now vows to right economic problems dating back decades - but has just five years.
A bishop since 1994, he resigned the post in December 2006 to sidestep Paraguay's constitutional ban on clergy seeking office.
With about 13,000 of 14,000 balloting stations counted late Sunday, officials said Lugo had 41 percent of the vote, Ovelar had 31 percent and former army chief Lino Oviedo had 22 percent. Given Lugo's commanding lead, Ovelar conceded defeat.