The goal of a broad coalition will not be an easy one, however, and will force Netanyahu to make some difficult decisions. In an interview last week with The Associated Press, Lapid said he would not be a "fig leaf" for a hard-line agenda on peacemaking. A leading party member, Yaakov Peri, said Wednesday that Yesh Atid will not join unless the government pledges to begin drafting the ultra-Orthodox into the military, lowers the country's high cost of living and returns to peace talks.
"We have red lines. We won't cross those red lines, even if it will cost us sitting in the opposition," Peri told Channel 2 TV.
That stance could force Netanyahu to promise overtures — perhaps far more sweeping than he imagined — to get peace negotiations moving again.
But a harder line taken by traditional and future hawkish allies could present formidable obstacles to coalition building.
Experience also shows that promises made during coalition negotiations do not always pan out. Centrist parties have been drawn before into coalitions dominated by hawks, only to bolt later in frustration over impasses in peacemaking. Yesh Atid has not yet spelled out specific conditions it would set down on this issue.
The election results surprised Israelis, given the steady stream of recent opinion polls forecasting a solid hard-line majority and a weaker showing by centrists. Netanyahu may have suffered because of his close ties to the ultra-Orthodox and perhaps from complacency. Many voters chose smaller parties, believing a Netanyahu victory was assured.
Statistician Camil Fuchs, who conducts polls for Israeli media, said previously undecided voters who had accounted for up to 23 percent of those questioned in opinion surveys, threw their support to Lapid in large numbers. Pollster Mina Zemah said support surged for Lapid in the last few days of the campaign, and he drew about 50 percent of his support from the right.
Lapid said the election outcome reflected a longing for unity in a country beset by schisms.
"That is the message that the results of the elections have sent us," he told cheering supporters. "The citizens of Israel today said no to politics of fear and hatred. They said no to the possibility that we might splinter off into sectors, and groups and tribes and narrow interest groups. They said no to extremists, and they said no to anti-democratic behavior."
Tensions with the United States, Israel's most important ally, also may have factored into the shift to Lapid. President Barack Obama was quoted last week as saying that Netanyahu was undermining Israel's own interests by continuing to build Jewish settlements on occupied lands the Palestinians want for a future state.
Netanyahu has won praise at home for drawing the world's attention to Iran's suspect nuclear program and for keeping the economy on solid ground at a time of global turmoil. But he has repeatedly clashed with international allies over his handling of the peace process, which has stalled over the issue of Israel construction in Jewish settlements in the war-won West Bank and east Jerusalem.
The Palestinians want Netanyahu to halt all settlement construction as a condition for talks. But the Israeli leader says talks must start without preconditions and notes a 10-month slowdown he imposed earlier in his term did not encourage meaningful negotiations.
On Wednesday, the Obama administration said the U.S. approach to the Israeli-Palestinian conflict would not change, regardless of the Israeli election results.