Khalil Al Hayya's election as head of Hamas's political bureau, the top post in the Palestinian group, was achieved by the narrowest of margins, beating rival Khaled Meshaal by one vote.
Sources with direct knowledge of the electoral process said 35 members of the group's Shura Council voted for Mr Al Hayya and 34 for Mr Meshaal.
The Shura Council comprises representatives of the Gaza Strip, the Israeli-occupied West Bank and the Palestinian diaspora, and operates in a manner similar to that of a parliament.
The political bureau, on the other hand, is Hamas's top executive body whose head is viewed as the group's supreme leader.
Mr Al Hayya "won it on the back of votes cast by Shura Council members from the Gaza Strip", said one of the sources. "It shows the weight of Gaza in the group and signals its resolve to continue as a resistance movement."
Mr Al Hayya is widely associated with the Hamas-led October 7, 2023 attacks on southern Israeli communities, which triggered a devastating military response from Israel that has to date killed more than 73,300 Palestinians in Gaza and reduced much of the territory's built-up areas to rubble.
It is thought his prominent role helped him in the vote.
Israel's military actions in Gaza have given rise to accusations of genocide, which it denies.
Mr Al Hayya's hardline ideology may not bode well for the future of US President Donald Trump's peace plan, which paused two years of war between Hamas and Israel last October but has since stalled over Israel's insistence that Hamas fully and unconditionally disarm.
Mr Al Hayya served as the group's lead negotiator in talks to implement the US peace plan for Gaza. The new Hamas leader has made it clear to mediators from Egypt, Turkey and Qatar that the group will stick by its demand that its members keep firearms for personal protection after giving up heavy weapons to the custody of the mediators. He also demands that Israeli-backed militias in Gaza must simultaneously disarm.
Mr Al Hayya replaces Yahya Sinwar, who is believed to have masterminded the 2023 attacks, when about 1,200 people were killed and another 250 abducted. Mr Sinwar, like Mr Al Hayya a founder of Hamas, was killed by Israeli troops in October 2024 after a prolonged manhunt.
Mr Sinwar himself had taken on the group's leadership after Ismail Haniyeh was killed in an attack on an Islamic Revolutionary Guard Corps guesthouse in Tehran on July 31, 2024. The attack has widely been blamed on Israel.
Before his election this week, Mr Al Hayya was a member of a five-man leadership council that had led Hamas since Mr Sinwar was killed. A native of Gaza, he has lost several close relatives, including his eldest son, to Israeli strikes on the Palestinian territory.
He survived an Israeli air strike on Hamas's office in Doha last year, in which five members of the group, including another of his sons and a Qatari officer, were killed.
The sources said Mr Al Hayya, along with senior members of the political bureau, have spent little time in the Qatari capital since the attack in September, preferring to remain in Turkey, which they see as a safer option for now.
In the run-up to his election, Mr Al Hayya served as the group's chief negotiator, leading Hamas's team in round after round of talks with the mediators to push forward Mr Trump's peace plan.
Those talks have yielded no results, with Washington preoccupied with the Iran war.
Mr Al Hayya takes over at a time when Hamas is reeling from Israel's continuing attacks, targeting its military and political leaders.
With layers of its leadership now eliminated, Hamas's military capabilities have diminished as it is facing a growing threat from Israeli-backed militias.
The election of Mr Al Hayya should end the feud between his faction and that of Mr Meshaal, at least temporarily. The election was held only to fill posts that became vacant after killings by Israel and another ballot will be held next year, possibly resurrecting the rivalry.
