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SAN SALVADOR, El Salvador — El Salvador's new president-elect won in resounding fashion, but breaking the three-decade hold on power of the country's two dominant parties means that Nayib Bukele will take office with few friends in Congress.

The 37-year-old former mayor has an ambitious agenda, topped by a vow to root out corruption. To accomplish that and many other campaign promises, Bukele will have to find allies who can help.

Bukele won with more than 53 percent of the votes Sunday, topping three rivals. But GANA — the Grand Alliance for National Unity party that he carried to victory — has only 10 seats in the legislature, well short of the 43 votes needed to pass laws.

"This new government is going to be weak," said Alvaro Artiga, a professor of political science and sociology at the Jose Simeon Canas Central American University. "It's that institutionally it doesn't have legislative support."

The outgoing Farabundo Marti National Liberation Front, or FMLN, government had a difficult time of it as a minority presence in the Legislative Assembly, and it had 23 of the 84 seats.

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And Bukele's promise to establish a commission to investigate official corruption modeled on a U.N.-backed effort in Guatemala is unlikely to win him friends among the FMLN or the conservative Nationalist Republican Alliance, or ARENA. That party itself has 37 deputies and its allied parties have 12 more.

Bukele will need to send a message immediately through his cabinet picks that it won't be business as usual, and avoid cronyism, Artiga said. "It can't be the friends, the relatives, all that he has accused the usual suspects of," he said.

"He can't repeat that, because people voted as a rejection," Artiga said. Bukele will start his five-year term June 1.

El Salvador is small both in size and population, with just 6.5 million people. Close to a third of its households live in poverty, and Salvadorans searching for a better life have joined recent caravans of migrants trekking across Mexico hoping to reach the U.S.

Bukele rose quickly through the ranks of the FMLN, a former guerrilla army that transformed itself into a political party after a 1992 peace deal ended the nation's civil war. He first won election as a youthful small-town mayor and then became mayor of San Salvador, the capital. But his persistent criticisms of FMLN leadership got him expelled from the party. Joining GANA — which has been a right-leaning party — was a last-minute move just to get on the ballot.

"It was always about the size of the resentment among the urban middle class toward the country's elites," said political analyst and former guerrilla commander Salvador Samayoa. "It was never that he was the best, most honest, most wholesome, most capable candidate."

Voters were tied of corruption, the lack of economic opportunities and the persistent violence.

"I voted, everybody in my family voted for Bukele because we're tired of these ARENA and FMLN governments that steal money," said 42-year-old Manuel Lopez as he headed to work Monday. "Nobody believes them."

"Two presidents from ARENA, Paco Flores, Tony Saca and one from FMLN, Mauricio Funes, have stolen everything they could," he said.

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