A senior Hamas leader this month declared that any deal to end the fighting in Gaza must include the release of Marwan Barghouti. Three weeks before, a former Israeli security chief had identified Marwan Barghouti as “the only leader who can lead Palestinians to a state alongside Israel.”

His name may not be familiar to many Americans. But most Palestinians, whether in the West Bank or in Gaza, know it well. So do many senior Israelis. Thirty or so years ago, Mr. Barghouti was among the most promising of a new generation of Palestinians poised to succeed Yasir Arafat, the revolutionary who had led the Palestinians through armed resistance to a measure of self-rule.

For most of the years since, Mr. Barghouti, a figure in Mr. Arafat’s Fatah party, has been in an Israeli prison, serving several consecutive life sentences for murder and for membership in a terrorist organization. During that time, his popularity among Palestinians has continued to grow; today he consistently leads surveys of Palestinians in the West Bank and in Gaza on who should lead them next.

It is hard to imagine that Prime Minister Benjamin Netanyahu, a hard-line opponent of Palestinian statehood whose government includes virulent Israeli nationalists, would ever assent to the release of Mr. Barghouti. And in their fury and anguish over the vicious Hamas attack on Oct. 7, most Israelis would probably agree.

But the search for a Palestinian leader has become more pressing, as the attention of Israel’s allies and its Arab neighbors turns to “after Gaza,” as Israelis refer to what will follow the extraordinarily destructive and deadly war there. Negotiations involving the United States and Arab states for a way to stop the fighting are intensifying, and one crucial unresolved question is whether there is anyone not linked to Hamas or the corruption in the Palestinian Authority who could take charge in a ravaged Gaza and replace the unpopular leader in the West Bank, the 88-year-old Mahmoud Abbas.

In an interview with The Guardian last month, Ami Ayalon, a highly decorated Israeli official who had served as naval commander in chief, head of the internal Shin Bet security service and cabinet member, said that man is Marwan Barghouti, now 64. “Look into the Palestinian polls,” Mr. Ayalon said. “He is the only leader who can lead Palestinians to a state alongside Israel. First of all because he believes in the concept of two states, and secondly because he won his legitimacy by sitting in our jails.”

Why Hamas, a radical Islamist movement with a history of conflict with Fatah, the movement in which Mr. Barghouti was reared, might seek his release is less clear. One line of speculation among Israelis is that the exiled political leadership of Hamas, headed by Ismail Haniyeh from Qatar, may believe that securing the freedom of the popular Mr. Barghouti would help salvage the group’s standing among Palestinians after the catastrophic war.

I first encountered Mr. Barghouti in 1996, when I was the Times bureau chief in Jerusalem and he was a new member of the Palestinian Legislative Council, created as part of the partial self-rule granted the Palestinians by the Oslo Accords. A small, intense man of 37, quick to smile, he was always available to reporters and huddled frequently with colleagues in the halls. He soon built close contacts with Israeli politicians and members of the peace movement, then still robust. The Oslo Accords, he told me, were “the biggest step in our history.”

He had come to the Council by a path familiar to many of his contemporaries: He was 15 when he was first detained, he wrote; in 1978, at age 19, he was sentenced to prison and endured the ordeal of torture and interrogations, which he later described as an “illegal system of mass arbitrary arrests and ill-treatment.” But he also used the time in prison to finish secondary school and learn Hebrew. When he completed his sentence, he enrolled at Birzeit University in the West Bank, a hotbed of Palestinian student activism, and became one of the major leaders in the West Bank of the uprising known as the first intifada.

Arrested and deported to Jordan in 1987, he returned to Israel under the terms of the Oslo Accords and was elected to the Legislative Council. In an article for The Times Magazine in August 1996, I listed Mr. Barghouti among a group of young, charismatic and energetic members of the Council — “Arafat’s Heirs.” Unlike Mr. Arafat and his cohort, who had worked and fought from exile, Mr. Barghouti and the others had grown up in the West Bank or Gaza and were intimately familiar not only with life under occupation, but also with the achievements and history of the Israelis. Many spoke and were familiar with the freewheeling give-and-take of Israeli democracy, which they sought to emulate in their own government.

The young Palestinians were even prepared to challenge Mr. Arafat and his old guard, driving the autocratic chief to fulminate, threaten and even stalk out of Council meetings. At one session, the young legislators demanded that Mr. Arafat, who had just ordered several hundred militants of the Hamas and Islamic Jihad movements detained over a spate of bombings, follow the laws of the new Palestinian Authority and make the detainees’ names and charges public. To Mr. Arafat, accustomed to unquestioned obedience in secretive organizations, this was incomprehensible, especially as Israel and the United States applauded the roundup.

The idealism of Mr. Barghouti and his peers soon faded, as the process that Oslo was meant to initiate foundered. Before long, Mr. Barghouti was at the barricades again, ready to exhort Palestinians to use force against Israel. In 2002, he was arrested and brought to trial in a civilian Israeli court on charges of murder and terrorism. At his first court appearance, he refused to cooperate and instead shouted in Hebrew that he wanted to present his own charges against Israel. The second appearance was even more tempestuous, but in the end, Mr. Barghouti was sentenced to five life sentences and an additional 40 years — the maximum possible penalty.

With the help of his wife, Fadwa Barghouti, a lawyer, Mr. Barghouti has remained politically active and vocal from prison, alternating between visions of coexistence and calls for resistance. He organized a hunger strike of Palestinian prisoners in several Israeli jails in 2017, which he described in a guest essay in The Times.

Last August, Ms. Barghouti was reported to have held meetings with senior officials and diplomats from the United States, the Arab world and European countries to lobby for her husband’s release so that he could succeed Mr. Abbas as head of the Palestinian Authority. The meetings are said to have included the foreign ministers of Jordan and Egypt and the secretary-general of the Arab League, but no details have been made public.

It is difficult to envision Mr. Barghouti’s release in the current situation — particularly with Mr. Netanyahu’s grip on power so far intact. But then, there was a time when Mr. Arafat’s return to Israel as acknowledged leader of the Palestinians seemed equally impossible.