(CNN) -- Mauricio Funes, a member of a political party that waged guerrilla war against the government 17 years ago, claimed the presidency of El Salvador on Sunday night.



FMLN's Mauricio Funes shows his ballot before voting Sunday in Antiguo Cuscatlan, El Salvador.



"This is the happiest night of my life," Funes told a jubilant crowd at his election headquarters. "It's also the night of greatest hope for El Salvador."



With 90.68 percent of the votes counted, the FMLN party's Funes had 51.27 percent, while the ARENA party's Rodrigo Avila had 48.73 percent, the country's Supreme Electoral Tribunal said.



The final tally will be certified within 48 hours, the electoral council's Walter Araujo said in a nationally televised news conference.



Funes' victory ended a 20-year hold on the presidency by the right-leaning ARENA.



"Now the ARENA party passes into opposition," Funes said. "ARENA ... can be assured that it will be listened to and respected."



Although polls had indicated the race had tightened considerably in the past few weeks, most analysts had predicted that Funes would win.



"It's a sign that there's democracy in that country, which is something the United States tried to foster," said Bernard Aronson, who as President George H.W. Bush's assistant secretary of state for inter-American affairs from 1989-93 was heavily involved in ending El Salvador's 12-year civil war.



The FMLN, which is the Spanish acronym for the Farabundo Marti National Liberation Front, was formed in late 1980 as an umbrella group for five leftist guerilla organizations fighting a U.S.-backed military dictatorship. The guerrillas and the government signed a peace pact in 1992 and the FMLN became a legitimate political party.



By some estimates, 75,000 Salvadorans died during the war.



The new president will find "a country that still retains a lot of bitterness, a lot of division," said Peter Hakim, president of the Washington-based Inter-American Dialogue policy institute.



"This country is completely divided," ARENA party official Adolfo Torres said on CNN affiliate TCS TV station Sunday night.



The election, Hakim said, was "an important test of how far El Salvador has come."



The result also will be an important test of how far El Salvador will go.



With an economy in deep trouble and neither party having enough seats to control the national Legislative Assembly, much will depend on the party that lost.



"Conflict occurs when one person wants to force a conflict," Hakim said. "Compromise requires both sides."



No one is certain how ARENA will handle the loss.



"That's a big unknown," said Heather Berkman, a Latin America analyst with the consulting firm Eurasia Group. "I still think they'll play ball. They have an incentive to get along with the new administration. They certainly don't want to be shut out of the process."



Otto Reich, who served in high-level Latin American posts for Presidents Reagan, George H.W. Bush and George W. Bush, sees the possibility of a spirited fight from ARENA.



"If I had to guess, I'd say ARENA will try to put democratic obstacles in the way of an FMLN consolidation of power," Reich said.



Although ARENA, which are the Spanish initials for the Nationalist Republican Alliance, has come back from a 14-point deficit in some polls two months ago, Reich said winning a fifth consecutive term was "swimming against the tide."



"People in El Salvador are weighing risks and opportunities," Reich said. "They have an opportunity to replace a party with which they have gotten tired."



Hakim also saw voter fatigue with ARENA, saying, "One party has managed the country forever and ever."



Many of the 2.4 million Salvadorans who voted weighed competing doubts.



"The uncertainty is that the FMLN has never been in power," Berkman said.



But voters also asked themselves, she said, whether they were "better off than they were five years ago,
What would end 20-year hold by the right-leaning ARENA? What percentage of vote did he have? Who had 51.27 percent of the vote how many ballots were counted When did he last win? what would the victory end Who died during the civil war?
Funes' victory 51.27 Funes 90.68 percent Sunday a 20-year hold on the presidency by the right-leaning ARENA. 75,000 Salvadorans
question: What would end 20-year hold by the right-leaning ARENA?, answer: Funes' victory | question: What percentage of vote did he have?, answer: 51.27 | question: Who had 51.27 percent of the vote, answer: Funes | question: how many ballots were counted, answer: 90.68 percent | question: When did he last win?, answer: Sunday | question: what would the victory end, answer: a 20-year hold on the presidency by the right-leaning ARENA. | question: Who died during the civil war?, answer: 75,000 Salvadorans