Mr. Pannella in 1997. (Andrew Medichini/AP)

Marco Pannella, a political provocateur who, as a co-founder and longtime leader of Italy’s Radical Party, used hunger strikes to help spur the legalization of divorce and abortion in his country, died May 19 at a clinic in Rome. He was 86.

He had liver and lung cancer, according to Italian media, which reported his death.

In the seven decades since World War II, dozens of governments have formed and fallen in Italy, where the long-dominant Christian Democrats squared off against the Communists and an array of other parties in what at times seemed a continuous political melee.

A constant amid the turbulence was Mr. Pannella, a consummate showman, protesting, striking, holding court and holding forth. He served in the Italian Chamber of Deputies, the lower house, from 1976 to 1994 and in the European Parliament from 1979 to 2009.

Founded in 1955, the Radical Party promoted itself over the years as a challenge to the entrenched and often corrupt Italian political establishment and to the influence of the Catholic Church. Its platform included expanded rights for women, gays and lesbians, prisoners and conscientious objectors, as well as the legalization of marijuana and euthanasia, disarmament, and the discontinued use of nuclear energy.

Mr. Pannella protests outside St. Peter’s Basilica in Rome in 2007. (Sandro Pace/AP)

News reports over the years described Mr. Pannella as “eccentric” and his party as “quixotic.” In elections, the party polled in the single digits. What Mr. Pannella did not win in votes he won in affection, endearing himself to the public in Italy and beyond with his spunk.

He drew international headlines for his hunger strikes, which sometimes lasted months, and which he used most effectively in the 1970s to force parliamentary debates on divorce and abortion, both of which were opposed by the Catholic Church.

Italians affirmed a law permitting divorce in a historic 1974 referendum. Abortion in some circumstances was legalized in 1978 and affirmed three years later in a referendum.

Mr. Pannella’s protests sometimes took the form of stunts. He once played Robin Hood to protest public financing of campaigns, distributing a total of $148,000 to thousands of citizens in the northern city of Treviso and telling them that it was money “stolen by the parties from the Italian people.” The source of the money was not reported at the time.

In 1995, he donned a Santa Claus costume and distributed hashish in Rome’s Piazza Navona in protest of drug policies that he said indirectly benefited the Mafia. Two decades earlier, he had been arrested for partaking publicly of the drug, declaring at a news conference, “This is 1.5 grams of what I believe is rather good hashish,” the New York Times reported.

In 1979, he and a reported 8,000 followers descended on St. Peter’s Square on Easter Sunday, during Pope John Paul II’s “Urbi et Orbi” address, to draw attention to world hunger. In what was interpreted as a nod to the group, John Paul said in his remarks that he was thinking “of all those who are suffering for the lack of what is strictly necessary for existence and of all those who suffer hunger, and above all of the little children.”

Upon Mr. Pannella’s death, a Vatican spokesman, the Rev. Federico Lombardi, described the politician in a statement as “a person with whom we often found ourselves in the past in different positions, but whose total and disinterested commitment for noble causes could not fail to be appreciated.”

Giacinto Pannella, known as Marco, was born May 2, 1930, in Teramo, in the central Italian region of Abruzzo. His father was Italian and his mother was Swiss.

Mr. Pannella received a law degree from the University of Urbino in 1953 and worked as a lawyer and journalist before helping found his political party.

Mr. Pannella, who identified as bisexual, had a long relationship with Mirella Parachini, a gynecologist. A complete list of survivors was not immediately available.

For his nonviolent protest, the Times once reported, Mr. Pannella became known as the Gandhi from the Abruzzi. He did allow himself certain indulgences. He confessed to smoking 60 grappa-flavored Toscanello cigars a day and, during his hunger strikes, subsisted on vitamins and cappuccino.