Israel on Wednesday increased pressure on Hamas to free Gilad Shalit, the soldier held by the Gaza militants, by saying it would not agree to a long-term cease-fire deal, open borders into the coastal strip, or release the 1,000 prisoners that Hamas wants freed until they know he is coming home.

The Israeli Security Cabinet's stance angered Egyptian mediators and Hamas officials who say a prisoner swap, which appeared imminent, should be a separate issue from truce talks.

The decision may set back negotiations in Cairo and probably postpone the freedom of Palestinian prisoners – one of whom is an unexpected choice among the scores of Hamas inmates: Marwan Barghouti, the most popular man in Fatah.

Mr. Barghouti, arrested by Israel in 2002 at the height of the second intifada, has been consistently chosen in public opinion polls as man most Palestinians think of as their future leader, and the candidate most likely to beat Hamas in the next presidential election.

But why would Hamas work to see Barghouti set free?

Many here say that winning Barghouti's release will help Hamas win points among all Palestinian factions. Internally, this could pave the way to national reconciliation by helping to mend the bitter Fatah-Hamas split. Abroad, it's likely to blur the line between Palestinians who are ready to reach a permanent peace deal with Israel and those who will never be.

"Hamas wants to say, we are not against Fatah as Fatah. We are against the corrupt people and the collaborators, and we want what's best for all the Palestinian people. In this way, Barghouti's release will be very helpful for Hamas's image," says Qaddura Fares, a senior Fatah official, as he sits in a office like so many here, one with a huge picture of Barghouti. In it, Barghouti is wearing a brown Israeli prison uniform and raising victorious-but-shackled wrists – an image that can be seen in every town and village in the West Bank.

Despite the Israeli cabinet decision Wednesday, much progress has been made toward a prisoner exchange following the 22-day war between Israel and Hamas. That war came to an uneasy pause when both sides declared unilateral cease-fires on Jan. 18.

Since then, Israel and Hamas – with the help of Egypt – have been weighing a prisoner exchange, as well as an official truce that would have two important aspects: Israel would open border crossings into Gaza and Hamas would stop firing rockets at Israel.

But Israel now says nothing will happen without the release of Shalit.

Saad Nimr, who runs the campaign for Barghouti's release, says that Hamas officials have promised that Barghouti is at the top of the list for release, along with three other non-Hamas members among the 1,000 to 1,400 names they have presented to Israel.

"Marwan is no longer perceived as a leader in Fatah. He's considered a national leader," says Dr. Nimr. "Hamas realizes this, and they know that any deal to release prisoners that doesn't include him will be seen as totally pointless. The Israelis understand that this is the price they have to pay for Shalit."

Shalit was abducted by Hamas militants in a cross-border attack in June 2006 in which Hamas militants tunneled into Israel.

Like Yasser Arafat before him, Palestinians here say that Barghouti is an unassailable symbol of the struggle, holding a status that few others do. From extremely humble beginnings – he was born in a cave at a Ramallah-area shrine, Nimr says – he became a leader in campus politics and street uprisings, and was in and out of Israeli jails.

By the late 1990s, Barghouti was an outspoken force of the "young guard" at legislative council sessions, and grew surprisingly critical of Arafat's less-than-democratic restraints on the parliament. But after the second intifada broke out in 2000, Barghouti began vacillating between governance and guerrilla warfare. In 2004, an Israeli court gave him five life sentences for his role in as many killings of Israelis.

Today, people who know Barghouti say that he's both older and wiser. He spent much of his time in jail reading voraciously and writing perspicaciously: He recently finished a PhD dissertation on the Palestinian legislative council and sent it to Cairo University. Barghouti drafted the 2006 "Prisoner's Document," which brought members of all factions together – Hamas included – in support of negotiations leading to a two-state solution with Israel. He also helped forge the Mecca Agreement, which attempted to bring about a national unity government for Palestinians. And while he still represents secular-national Fatah, Barghouti speaks the language of resistance that has become the mainstay of Hamas, minus the Islamic ideology.

"The language of Marwan – resistance and struggle – is closer to Hamas," says Iyad Barghouti, a political analyst who is not directly related to Marwan.

To be sure, some in Israel oppose Barghouti's release. But his lawyers, as well as others close to him, say he is at the top of the list, and that Israeli officials are not totally opposed. The question of his release is now more a matter of when than if, says Barghouti's lawyer, Hader Skikerat. Israeli leaders have said in recent days that they will not comment on the Shalit-for-prisoners deal so as not to take a chance of scuttling it.

But those who are most concerned about Barghouti's release are senior Fatah officials close to Palestinian Authority (PA) President Mahmoud Abbas, known as Abu Mazen, who are concerned about the impact of suddenly having Barghouti back.

"The image among the people is that Marwan be stronger than Abu Mazen. And the question which is raised here, again and again, is if Abu Mazen was talking to the Israelis, why didn't he demand Marwan's release before?" explains Dr. Barghouti, the analyst. "As a result, there may be a conflict between Fatah and the Palestinian Authority, a kind of question of who is really in charge," because Marwan Barghouti is considered the most powerful man in the West Bank, while Abbas is seen as weak and ineffective.

"It's known that there are people in the PA who will not be happy with his release, or the release of the rest of the parliament members," says Barghouti.