JERUSALEM — Striking a secret deal with the leader of the opposition in the small morning hours, Prime Minister Benjamin Netanyahu of Israel significantly expanded his power on Tuesday, creating the largest and broadest coalition government in recent memory, one that no single faction can topple.

The question now is what Mr. Netanyahu plans to do with it.

Long seen as a pragmatist and master political tactician, Mr. Netanyahu has focused on minimizing risk — to Israel, and to his own standing. That posture has left many wondering what his true political priorities would be if, as has now come to pass, he was freed from the demands of more ideological factions within his coalition for the past three years.

With 94 of Parliament’s 120 seats, Mr. Netanyahu can claim a broad mandate, but few analysts here expect any significant shift in many of the major policy issues that have confounded resolution for decades, especially the evacuation of illegal settlements or an overall deal with the Palestinians.

At a news conference announcing the agreement with the centrist Kadima Party, Mr. Netanyahu listed “advancing a responsible peace process” among the new coalition’s four top missions, but was quick to reiterate his longstanding position that the process was stalled because of an unwilling partner, not lack of willingness within his camp. The prime minister’s aggressive focus on the Iranian nuclear program as an existential threat to Israel is even less likely to change, analysts said, since there is less disagreement on that issue with Kadima’s leadership.

Instead, many here think there will be movement on the domestic front, including an overhaul of the electoral process and an end to the widespread exemption of ultra-Orthodox Jews from military or national service. Mr. Netanyahu had long been hampered on those issues — which resonate deeply with the Israeli public and go to the heart of what kind of democracy the young state will become — by the right-wing and religious parties on which his smaller coalition had depended.

Some analysts have noted that the deal emerged barely a week after the death of Mr. Netanyahu’s 102-year-old father, a scholar and hawkish Zionist whom many here thought he had been loath to offend with compromises on settlements and other issues.

Several people close to the prime minister gave their positive assessment, saying the new coalition, whose largest bloc is Kadima’s 28 seats, is better aligned with Mr. Netanyahu’s personal politics than the right-leaning one he had led since his election in 2009.

“I think Prime Minister Netanyahu has been determined since he got elected to re-establish a very strong political center in Israel,” said Dore Gold, president of the Jerusalem Center for Public Affairs and an adviser to Mr. Netanyahu during his first term as prime minister, in the 1990s. “What does it mean to be in the center? It means willing to make compromises to ensure peace, but at the same time insisting that any arrangement you make has a large security component.”

But others saw the coalition as a crass political move, one aimed exclusively at enhancing Mr. Netanyahu’s political power rather than advancing a more moderate or compromising agenda. Late Tuesday, more than 1,000 demonstrators, including the ousted Kadima chief, Tzipi Livni, marched in Tel Aviv in protest of the alliance.

The agreement, signed just after midnight Tuesday at the prime minister’s home in Jerusalem, makes the newly elected chairman of Kadima, Shaul Mofaz, a deputy prime minister who will stand in for Mr. Netanyahu when he is abroad and sit in on all closed cabinet sessions that “deal with security, diplomatic, economic and social issues.” It was signed even as members of Parliament were huddling in committee hearings late into the night on legislation to dissolve the government in preparation for elections slated for Sept. 4 rather than when its term expires, in October 2013.

On Sunday evening, with the issue of the military exemption threatening to split his coalition, Mr. Netanyahu had called for the early elections in a speech to the convention of his Likud Party, saying he wanted to avoid the instability of a long campaign. By Tuesday at noon, he said at a news conference that he had “realized it was possible to restore stability without holding elections.”

The new coalition is “good for the security of Israel, good for the economy of Israel, good for the society of Israel and good for the people of Israel,” said Mr. Netanyahu, slightly hoarse and clearly exhausted from a long night of negotiations, but in good humor.

Mr. Mofaz, a former defense minister and military chief who even in the days leading up to the agreement had vowed not to join Mr. Netanyahu’s government, said the new coalition would be able to “contend better with the challenges facing Israel,” including “a historic territorial compromise with our Palestinian neighbors.”

Nabil Abu Rudeineh, chief spokesman for the Palestinian president, Mahmoud Abbas, said the new coalition could present new opportunities — but in the next breath reiterated the positions about settlements, borders and Jerusalem that have been stumbling blocks in the past.

“If they are serious and willing,” he said of the Israelis, “this is the right moment.”

But Mr. Abu Rudeineh said cessation of all settlement activity was essential “to bring a sense of seriousness to the table,” adding that “the 1967 borders with agreed swaps and East Jerusalem as a capital” had to be the basis for negotiations.

The secret deal stunned the political establishment here, and led to swift, harsh denouncements from the dwindling opposition and a few of the old coalition members.

Isaac Herzog, a leading Labor Party member of Parliament, described his Kadima colleagues as “28 midgets” and accused the prime minister of having “a fear of heights,” promising, “The public will hate it and will pay a price for it.”

Danny Danon, the only member of Likud’s delegation to vote against the deal, predicted: “It’s only a matter of time until this wedding will collapse. Within 18 months we know they will go to file the divorce papers, and I think it will be before 18 months.”

But political analysts, while equally surprised by the deal, described it as deft maneuvering by both men.

For Mr. Mofaz, whose Kadima Party was expected to lose up to half of its seats if elections were held soon, it is a critical lifeline, elevating his status and giving him more time to build up public support before the next election. There is, however, the risk he will have damaged his credibility because he had previously said he would not join forces with Mr. Netanyahu.

As for the prime minister, the veteran journalist David Horovitz called it a “masterstroke” while Amit Segal, Channel 2’s commentator, named it “the deal of the century,” saying Mr. Netanyahu got Mr. Mofaz for “half price” and 27 other lawmakers free.

Another clear winner is Defense Minister Ehud Barak, who has grown increasingly close to Mr. Netanyahu, particularly on the issue of Iran. A member of the tiny Independence Party, Mr. Barak faced an unclear future at the polls, and the deal allows Mr. Netanyahu to keep him by his side without upsetting Likud members by offering him a seat on their list.

While both Mr. Netanyahu and Mr. Mofaz promised changes on the draft question and on electoral reform, they offered specifics on neither. They are also under pressure on the question of Jewish settlements in the West Bank, facing a court-ordered July 1 deadline to dismantle one called Ulpana that the right wing has vowed to protect.

“He’s in a stronger position to negotiate both with the settlers and with the Supreme Court, and with his Likud rebels,” said Daniel Levy, a British-Israeli political scientist.

After a roller-coaster week that began with the poignant drama of the senior Mr. Netanyahu’s funeral and escalated into a frenzy over early elections only to erupt early Tuesday with news of the unexpected pact, the dynamics shifted suddenly to one of watch and wait.

“The prime minister can now pursue a much more ambitious set of foreign and domestic policies if he wishes,” said Robert M. Danin, a fellow at the Council on Foreign Relations. “On the other side, it will be much harder for him to suggest that he is constrained from taking certain steps.”

Gadi Wolfsfeld, a professor of political communication at the Interdisciplinary Center in Herzilya, said that “unless Netanyahu has really changed his mind about things, I’d be surprised if he really moved forward the peace process.”

“Then again,” Mr. Wolfsfeld added, “I was surprised last night.” Isabel Kershner contributed reporting. (Copyright 2012 The New York Times Company 05/09/12)