Franciso Sa Carneiro, the conservative victor in Portugal's national and local elections held two weeks apart this month makes it clear that he is prepared to press on all the most explosive issues in Portuguese politics.

His confrontational approach as leader of the center-right opposition apparently appealed to an electorate rhetoric surrounding most of the previous 11 cabinets in the five years since "the revolution of the carnations" overthrew the half-century of rightist dictatorship.

His approach led to the election of the first parliamentary majority that looks as if it will last.

Yet, Sa Carneiro insisted in an interview that attacking everything in sight -- military-backed President Antonio Ramalho Eanes, the constitution, the Socialists, who prevented a Communist takeover, and the growly influential Communists themselves -- is a thing of the past. "The style is different," he said, "for a leader of the opposition and a leader of the majority, the prime minister."

In the political and military elite that led the country out of the dictatorship of Antonio Oliveiro Salazar there is much genuine-seeming skepticism about Sa Carneiro's capacity for moderation, even though there is general recognition that it is in the future premier's own interest to be as statesmanlike as possible to lead his conservative coalition to reelection when parliament's term expires in less than a year.

"Good sense might prevail," said an intimate of President Eanes. "I hope so. Theoretically, everything can go well. In practice, we'll see. Sa Carneiro's statements so far have been responsible. Everything seems to be going well, maybe too well."

A member of the Revolutionary Council, the group of military men who still pass on the constitutionality of laws, said he had no doubts about Sa Carneiro's genuine intellectual commitment to democracy, but, he said, he is afraid of his "authoritarian personality."

The 45-year-old Sa Carneiro first made his mark by refusing to play along with the tame role in the official parliamentary opposition under Salazar.

Sa Carneiro sponsored a series of measures with no chance of adoption such as a bill abolishing press censorship and a demand for an investigation of police abuses. In 1973, the year before the revolution, he resigned his seat in parliament -- a gesture still considered courageous.

It was only the first of several resignations that wound up paying off for Sa Carneiro. He has seemed to be in search of a leading role for a long time, first as a champion of the center-left, now of the center-right. He has always refused to be subordinate to anyone. Sharing the limelight does not seem to come naturally to him, even though he is now making obvious efforts for the sake of keeping his coalition together.

Twice, Sa Carneiro resigned as leader of his own party, the Social Democrats. Both times it was only a tactical retreat after which he eliminated his adversaries and came back stronger than before, turning weakness into strength.

It is a commonplace to hear his combativeness attributed to his need to compensate for his shortness. He is ofter referred to as "a rooster." Always immaculately tailored, he is variously estimated to be 5 feet 2 inches. His thick-heeled shoes make it hard to judge.

Sa Carneiro's sensitivity seems to have had more to do with his bad relations with the last U.S. ambassador, Deputy CIA Director Frank Carlucci, than substance.

The Portuguese leader described how he refused to attend a Lisbon dinner in honor of Vice President Mondale. He said he was miffed over first being asked by Carlucci's embassy to meet separately with the visiting American and then being told that the vice president had decided against any separate sessions with leaders of the opposition to the government of Mario Soares, then the Socialist premier being heavily backed by Washington as the best barrier to the Communists.

Sa Carneiro described his relations with the equally diminutive Carlucci as "quite cold." The relationship became entangled in Sa Carneiro's complicated personal life when his outspoken companion of many years, Snu Bonnier Abecassis, berated the U.S. ambassador at a diplomatic dinner in the presence of other envoys for his alleged hostility to her man.

"Frank felt it was just about time for him to go when he left Portugal," said one of his colleagues. Part of the problem was apparently that Carlucci underestimated Sa Carneiro's ability to get to the top. Portugal's next premier recalls that the ambassador told him it was impossible to arrange requested meetings for him with top Carter administration figures when he visited Washington in 1977.

The United States is not the only natural ally that Sa Carneiro has defied. The Roman Catholic Church backed him heavily in the elections, but not because it could have any particular illusions about his attachment to Catholic tradition.

Sa Carneiro's wife lives with their five children in his native town of Oporto, the northern Portuguese bastion of conservatism.

He spends his time in Lisbon with Abecassis, a 39-year-old blond divorcee and mother of three. A member through her Swedish mother of the great Stockholm publishing family of Bonnier, the Danish-born Abecassis is herself one of Lisbon's leading book publishers with her now perhaps inappropriately named company, the Don Quixote Press.

She was often present on the sidelines of the Sa Carneiro campaign trail and the couple let themselves be photographed together on the way to vote on election days. There is much speculation about whether she will now become his social hostess.

By attacking President Eanes, elected with 61 percent of the vote as the official candidate of the armed forces, Sa Carneiro defied all the conventional wisdom of Portuguese politics and got away with it. Eanes seems to be boxed in by the future premier. A clash seems inevitable over Sa Carneiro's insistence on introducing the right to hold national referendums, which Eanes has already said would be unconstitutional. In that conflict, it is clear that Sa Carneiro would have the advantage of being able to accuse the president of wanting to restrict democracy.