Right-wing candidate Diogo Freitas do Amaral won a first-round victory today in voting for Portugal's first civilian president in 60 years. But he fell three percentage points short of the 50 percent needed for an outright victory.

The former Christian Democratic leader, who is backed by the center-right government, will face Socialist leader Mario Soares in a run-off election in three weeks. Soares, one of three left-wing candidates, placed second with 25 percent of the vote.

Freitas do Amaral's first-round total of 47 percent marked the farthest swing to the right by Portuguese voters since left-wing Army captains toppled a 48-year right-wing dictatorship in the 1974 "revolution of the carnations."

Both surviving candidates have said that the election will determine whether Portugal can rise above its recent history of political upheaval and economic stagnation.

"Portuguese politics will never be the same," said Soares. "Voters have rejected the radical left and chosen tolerance and dialogue."

Soares, three times prime minister since the revolution, surpassed by four percentage points his main left-wing rival, dissident Socialist Francisco Salgado Zenha, who was supported by outgoing President Antonio Ramalho Eanes, a retired general, and the pro-Soviet Communist Party.

Zenha's defeat reflected a loss of popularity for Eanes, who, after landslide victories in 1976 and 1980, was not eligible for a third term. Critics said he lost stature as an impartial defender of democracy after launching his own left-of-center political movement last year.

Left-wing independent Maria de Lourdes Pintasilgo polled 7 percent of the vote.

"Soares and democratic socialism have won the left-wing primary," said Socialist official Alvaro Barreto, referring to the contest among the three candidates who challenged Freitas do Amaral. "He will go on to defeat the right in the second round," Barreto said.

The Socialist leader is better placed in theory to win the run-off by accumulating the votes of the two other left-wing candidates. The left and center, although sharply divided, have commanded a majority of votes since the return to democracy.

But Soares is bitterly opposed by the Communists, who regularly poll 15 to 18 percent in elections and who have not committed their vote for the second round. They could choose to support neither candidate.

A principal issue was whether the new head of state would work with or against the minority Social Democratic government that came to power in an October election. "Freitas do Amaral is the only candidate who guarantees a constructive dialogue between the presidency and the government," said Prime Minister Anibal Cavaco Silva.

Previous conservative governments have accused the left-leaning Eanes of engaging in "institutional warfare" to block measures aimed at freeing the constitution and the economy from the leftist legacy of the revolution.

Eanes, a retired Army general who remained a pillar of stability during the collapse of 15 governments, the coup attempts and the economic crises that have marked Portugal's first 12 years of democracy, said he intervened only in defense of fundamental freedoms or to limit political upheaval.

All three left-wing candidates warned in their campaigns that the election of Freitas do Amaral would give political impetus to the extreme right and aggravate social tension. "Democracy will be under threat if Freitas do Amaral becomes president," said Zenha.

The 44-year-old law professor and former deputy prime minister denies such charges and has assumed a more centrist position since quitting the leadership of the right-wing Christian Democratic Party.

Freitas do Amaral's campaign themes were reprivatization of state industries, educational reform and ensuring political stability through harmony between the presidency and the government. "We can't go on changing governments every six months and leaving all our serious problems unsolved," he said.

If elected, Freitas do Amaral is expected to call an early legislative election this year in an effort to strengthen the position of the Social Democrats, who hold only 88 of the assembly's 250 seats. "The strategy would be to swing the rightward voting momentum quickly behind the government to achieve our formula for stability: a president, a government and a parliamentary majority," said a Cabinet member.

After three years of recession that has cut sharply into living standards, Cavaco Silva's four-month-old government has reanimated business confidence with measures to strengthen the currency, cut bank interest rates and lower taxes. Two days before the election, the government forecast economic growth of 4 to 5percent.

But big business is holding back investment until the outcome of the presidential election. "For us, there's a cloud over the economy that only the election of Freitas do Amaral will blow away," said the American manager of a subsidiary here.

Freitas do Amaral's first-round victory virtually was assured by the three-way split on the left. Soares, three times prime minister since 1974, campaigned as a mediator who could stop a damaging conflict between left and right. But critics say the Socialist leader's search for consensus on major issues has in the past led only to impasse and ambiguity.

Soares, 61, has been fighting an uphill battle since the Socialist vote fell by 16 percentage points to 21 percent of the total in the October election. But he is a skilled campaigner who has capitalized on a history of struggle against the pre-1974 dictatorship and his successful stand against a Communist push for power in the aftermath of the revolution.

"The pluralist democracy we have taken more than a decade to build is again at risk," he said in a campaign speech that warned of the dangers of the Communists or the extreme right gaining influence over the next president.