When the new Palestinian legislature is sworn in Saturday, Hamas's installation as the new majority will be hailed as an electoral milestone for the fledgling Palestinian democracy.
But a brewing dispute between the Islamic militants and the deposed Fatah Party is already calling into question the stability of a new government: How will authority be divvied up between the Hamas prime minister's cabinet and the higher-ranking post held by President Mahmoud Abbas?
"Palestinian legislation is slippery and elastic. There's unclear constitutional lines," says Bassem Ezbidi, a political science professor at Bir Zeit University in Ramallah. "We will have a power struggle from now on from these two heads of government. And that will impact everything: the mandate, the authority, the politics that will emerge."
Setting the stage for the standoff will be a speech expected by Mr. Abbas to lawmakers Saturday in which he'll ask Hamas, which calls for destruction of the Jewish state, to embrace his vision for peace with Israel.
Hamas is expected to remain steadfast in its opposition to Abbas's approach, deepening the divide between Fatah and Hamas lawmakers as negotiations begin to form the new government.
One of the most sensitive points of tension between the two parties is who will control the 60,000-strong Palestinian paramilitary police.
At stake is whether the policemen will reinforce Abbas's preference of extending a year-long calm in violence with Israel, or possibly collude with militants to launch new attacks.
Palestinian basic laws designate the president as a commander in chief. The prime minister is responsible for the national security council and appointing an interior minister - powers stripped away from the president three years ago to weaken the former Palestinian leader Yasser Arafat.
In its last session on Monday, the outgoing Fatah Parliament passed a law setting up a special court to resolve disputes between the prime minister and the president - a move condemned by Hamas.
But underlying the legal confusion are years of bad blood between the Islamic militant underground and the guerrilla leaders who Mr. Arafat installed as the security chiefs of the self-rule government when it was set up a decade ago.
Two weeks ago, a predawn blast on Suleiman Abu Mutleq's front stoop ripped a hole in his iron doorway and shattered the windows of his villa. The Khan Younis preventative security chief has yet to make an arrest, but has been quick to accuse.
"It's clear from the information we have that Hamas is responsible," says Mr. Abu Mutleq, who heads a force charged with pursuing militants who launch attacks on Israel. "They are acting blindly because they won. I don't understand how they can act like an opposition and form a government. It's unacceptable."
Although Hamas has denied involvement, Abu Mutleq's allegation reflects the mutual resentment between Fatah loyalists, who have dominated the Palestinian police, and newly elected Islamic militants who will now oversee security personnel who were once their jailers.
"How can they make a truce with Israel without giving political orders to arrest people?" asks Abu Mutleq. "No one from Hamas has shown up and said how they're going to manage the Palestinian street. There is something mysterious about it."
Indeed, there's a Pandora's box of questions about the future role of the police. If Abbas ordered security forces to disarm Hamas militants firing rockets into Israel, could the cabinet block the president? Will police chiefs continue to cooperate with Israel? Would a Hamas interior minister merge the movement's Izz-a-dine Al Qassem military wing into the police, only to still allow it to initiate strikes on Israel?
Hamas has paid lip service to unifying Palestinian militias with the security forces, but observers say they will wait before merging the Qassem brigades into the police.
A decade ago, Sheikh Ahmed Bahar was one of several Hamas leaders who were locked up in a crackdown by Arafat against the underground that dispatched suicide bombers to Israel. The newly elected Palestinian legislator said he hasn't forgotten the experience of nearly three weeks of torture, even if he has tried to forgive.
"I stayed 18 days, and I could barely open my mouth. They pulled out three fingernails and three toenails," he says. "There was a lot of anger [at the police]. We could escalate that issue, but we don't want internal fighting between the Palestinian people."
Mr. Bahar insisted that Hamas had gotten assurances from Abbas that the security services would be the province of the Interior Ministry. The Islamists will seek to collect illegal weapons, but will allow members of the "resistance" to arm themselves.
But Hamas also has a bone to pick with police chiefs who are widely suspected of corruption. "The security forces will be much better than they were before," says Bahar. "We will threaten the corrupt people who have stolen Palestinian money."
And yet, Hamas will have to tread carefully if it wants to give the security services a makeover.
That's because the ranks of the police are almost exclusively made up by Fatah. The same is true for other parts of the Palestinian government.
"They are the most important manifestations of the Fatah legacy. Fatah used to think of itself as the cream of the cream," says Mr. Ezbidi. "Those people have been exposed to the Fatah political culture, and Hamas knows to change the composition will take time. I don't rule out Hamas facing these challenges directly, and getting into clashes, and arm twisting."
At the Gaza police headquarters, Alaa Husni, the chief of the West Bank and Gaza civilian police, responds sarcastically when asked about whether he'd take orders from a Hamas interior minister. "What's the problem?"
"If Hamas is coming to create a conflict this will be unacceptable," he continues. "If they don't disarm themselves, if they don't stop distributing illegal weapons, they shouldn't be talking about security. If Hamas intends to annex the Palestinian security services to its militias, the general public will not accept this."