The coup, in which almost no shots were fired, became known as the Carnation Revolution after a restaurant worker and pacifist, Celeste Caeiro, offered carnations to the soldiers as civilians took to the streets to celebrate. Carnations were placed in the muzzles of the soldiers’ rifles and on their uniforms.

Mr. Freitas do Amaral’s party helped balance the far-left fervor, led by the Portuguese Communist Party, that surged after the dictatorship’s ouster. He played a central role in helping to steer Portugal away from its radical course in the post-revolution years, which coincided with the Cold War and triggered fears in Western Europe and the United States that the country, a member of NATO, might align with Moscow.

This year, President Marcelo Rebelo de Sousa described Mr. Freitas do Amaral as “one of the fathers of Portuguese democracy.” In 1980, The New York Times described him as “every inch a congenial but strict disciplinarian.” But in 2005, three decades after his founding role, he was shunned by the party he helped create when he accepted the post of foreign minister in a Socialist Party government. Christian Democrat officials took down his photograph from a wall in their Lisbon headquarters and mailed it across town to the Socialist Party.

Mr. Freitas do Amaral said he was never again invited to a party event.

After Portugal’s first parliamentary elections with universal suffrage in 1976, Mr. Freitas do Amaral served in a series of governments as deputy prime minister, foreign minister and defense minister. He was a key member of the Democratic Alliance, which drew moderates from various parties to stand together in a 1979 election. The Alliance won a majority in parliament .

In 1980, as both deputy prime minister and foreign minister, he briefly became head of government when Prime Minister Francisco Sá Carneiro , a 46-year-old Social Democrat, was killed along with six others when their small plane crashed into a house after taking off from Lisbon Airport on its way to a political rally.