By TIM WEINER
 
MEXICO CITY, March 21 — After a bitter campaign for president in El Salvador, a conservative pro-American businessman claimed victory Sunday night over a battle-hardened former Communist guerrilla.

The ruling party’s candidate, Antonio Saca, 39, a media mogul tacitly supported by the United States, was winning 57 percent of the vote in early returns. Schafik Handal, 73, a longtime left-wing leader, had 36 percent.

The campaign revived cold-war fervors from El Salvador’s civil war. An estimated 75,000 people died as an American-backed government fought left-wing rebels between 1980 and 1992.

Mr. Saca's party, the ruling Nationalist Republican Alliance, or ARENA, was linked to death-squad killings in the 1980's. Mr. Handal's party, the Farabundo Marti National Liberation Front, or FMLN, was the rebel force that fought the government. After a 1992 peace treaty, the FMLN became a legitimate political party, and now controls 31 of 84 seats, a plurality, in Congress.

American officials who were behind-the-scenes players in Central America's anti-communist campaigns during the 1980’s had openly opposed Mr. Handal.

Otto Reich, President Bush's special envoy for the Western Hemisphere, and Roger Noriega, an Assistant Secretary of State, inferred in public statements that El Salavdor's commercial, economic and political relations with the United States could suffer if the leftist won.

But ARENA has controlled power in El Salvador since the 1980's, and claimed that it kept control tonight.

President Francisco Flores is among the most pro-American leaders in the Western Hemisphere, and his apparent successor, Mr. Saca, has vowed to continue his policies, including free trade with the United States and adoption of the United States dollar as the nation's official currency.

ARENA, whose campaign colors are red, white and blue, argued that the United States could cut the flow of money from Salvadoran migrants in the United States if Mr. Handal won.

Mr. Handal promised to bring the 380-troop Salvadoran contingent home from Iraq, restore diplomatic relations with Cuba, tax the rich more heavily, increase government spending for the poor and still seek good relations with the United States.

Claiming victory tonight, Mr. Saca promised to govern for all, not only his supporters. This was the third presidential election since the 1992 peace accords; ARENA party candidates won both previous ballots. But neither peace nor the party have brought much prosperity to El Salvador. About a third of the people still live on about $1 a day, and a global drop in coffee prices has crushed small farmers. Hundreds of thousands of people fled the nation's violence and poverty over the past two decades.

Vilma Romero, 42, a doctor in San Salvador, the capital, chose Mr. Saca tonight, without enthusiasm.

"I'll stick with the devil I know," she said. "We're giving them another chance. This should be a big lesson for the right. They have to draw the conclusion that there are a lot of things that need to be fixed, and if they don't fix them, this will be their last chance."

Gene Palumbo contributed reporting for this story from San Salvador, El Salvador.