Portugal's ruling center-right coalition took a substantial lead in partial results from yesterday's general election, which saw a large turnout in a contest likely to affect the course of the fledging democracy.

With more than half of the vote counted, Premier Francisco Sa Carneiro's coalition had won 48 percent. The Socialists were running second with 26.2 percent and the Communists were third with 16.4 percent. The rest was divided among minor parties.

In voting last December that gave Sa Carneiro's Democratic Alliance a slim six-seat majority, the coalition won not quite 43 percent of the vote.

By increasing its share, the coalition hopes to claim a mandate to alter substantially the leftist constitution that emerged from the 1974 military overthrow of Portugal's right-wing dictatorship.

President Gen. Antonio Ramalho Eanes, who is backed openly by the opposition Socialist Party, obliquely criticized the government in a speech broadcast Saturday night by calling on the population to vote for moderation, and by warning of critical times and repression ahead if consensus politics did not continue to be the norm in Portuguese politics.

The Republican and Socialist Front, led by former premier Mario Soares, and the Communists have accused Sa Careiro of seeking to turn the clock back on the 1974 revolution during his 10 months in power.

Even before polling stations had opened, long lines began to form, reflecting the widespread concern about the vote. The greatest interest, however, centers on about a dozen marginal districts where the right narrowly wrested seats from the Socialists last December, giving them an overall majority in the 250-seat parliament.

In his broadcast Eanes somberly warned voters that "any radicalization of our political life will only bring about unreconcilable division and attempts at repression." The main thrust of Sa Carneiro's short term in office has been counteracting the excesses of the revolution and trying to return Portugal to a conservative market economy, closely allied to the West.

"Few can doubt," Eanes said, "that we will face a new wave of crisis in the next few years, probably more serious and complex than those we overcame in 1976," a reference to the date the Socialists regained control of the government after a period of Communist Party dominance and to the year when Eanes was elected president.

The president freely used key words, such as "dictatorship," that have a high emotional content for Portugal's 7 million electorate and compared the current international situation to that in Europe during the 1930s, when totalitarian parties came to power. His major theme was a call for agreement among parties.

"Only a solid basis of consensus, which democracy naturally guarantees, will allow a mobilization of all Portuguese for the common tasks," Eanes said.

The speech was clearly designed to set the stage for a return to coalition governments and to head off a conservative majority that, in the terms of Eanes and the left, will sharply divide the high politicized and economically backward Portuguese nation.

President Eanes, with the backing of the Sociualists, is standing for reelection in December and is as a clear front-runner to retain power against the candidate put forward by the Democratic Alliance, a conservative and little-known general, Antonio Soares Carneiro.

With fully reliable results not due until dawn, Lisbon remained largely empty and quiet last evening, with little sign of life other than at the churches and at the voting booths. Only the propaganda posters that fight for space on every available wall bore testimony to the enthusiasm and mass energy that marked the three-week long campaign. Outside the capital, the pattern of significantly high voter tunrout reflected that in the capital and there were no reports of violence.