The death of Oswaldo Payá has left a gap in the moderate heart of the Cuban dissident movement, which has tried for decades to figure out the most effective way to confront the communist system and push for democracy.

Payá was unquestionably the most centrist of Cuba’s opposition leaders, a profoundly Catholic activist who believed in reconciliation and dialogue, tried to change the system with its own rules and rejected both Fidel Castro and the U.S. embargo.

He was also the first opposition figure to try to mobilize the Cuban streets for change, while others focused on seeking political freedoms, establishing civil society groups or recording and denouncing human rights abuses.

“His death was truly an irreparable loss, because he was the most notable figure of the internal resistance,” Havana human rights activist Elizardo Sánchez Santa Cruz said of the 60-year-old Payá, killed Sunday in a disputed car crash.

The death also recalled the struggles of a man whose victories and failures as he tried to nurture the seeds of democracy in Cuba, peacefully and patiently, can provide lessons to the dissidents who survive him.

A soft-spoken and unassuming engineer who worked in a state-owned business making and repairing hospital equipment, Payá was “the anti-Fidel,” said Joe Garcia, a Miami Democrat and former executive director of the Cuban American National Foundation.

Although a Vatican official reportedly told U.S. diplomats in 2003 that he had urged the Cuban government to “cultivate Payá as a ‘soft oppositionist,’ ” government State Security agents constantly monitored his movements and his Havana home was often marked with pro-Castro graffiti.

Payá’s biggest triumph came in 2002, when his Christian Liberation Movement and a nationwide network of supporters collected 25,000 signatures seeking free elections, freedom of expression and association and amnesty for political prisoners in the so-called Varela Project.

He was praised by moderates who favored engaging the Castro government in hopes of pushing it gently toward democracy, was awarded the European Parliament’s Sakharov human rights prize in 2002 and was later nominated for the Nobel peace prize.

Payá “managed to mobilize people and unite the opposition in some ways,” said Guillermo Fariñas, an independent journalist who won the Sakharov Prize in 2010. Unlike Payá, Fariñas was not allowed to leave the island to pick up his award.

But Project Varela was criticized by anti-Castro hardliners in Cuba and in exile as too conciliatory toward the government — and was brutally crushed by Castro.

The legislative National Assembly of People’s Power never acknowledged Payá’s petition and Castro called his own referendum on the “irrevocable” socialist character of the revolution — approved by 99.5 percent of the voters in late 2002.

Just months later, 75 dissidents, including more than 40 Project Varela activists, were convicted in one-day trials and sentenced to up to 28 years in prison. Payá had spent three years in a hard labor camp in the 1960s but was not arrested in the 2003 crackdown.

The dissident soldiered on with the stubbornness of his faith after the so-called Black Spring but with less success, proposing several citizen initiatives that did not achieve the recognition or headlines of the Varela Project.