JERUSALEM – Egypt's first round of presidential voting wrapped up on Thursday with the crop of viable candidates down to just a handful. Official results won't be ready until Tuesday, but next door in Israel, policymakers are already scrambling to sort the bad options from the worse.

For all his faults, Egypt's President Hosni Mubarak was a reliable, if remote, Israeli ally for three decades until his ouster in a popular uprising last year. Subsequent parliamentary elections over the winter brought an Islamist rout, with the long-banned Muslim Brotherhood winning half of all seats and even harder-line Salafis taking another quarter. It's too early to tell if the next president will be an Islamist, but even if not, a new constitution could grant Egypt's formerly rubber-stamp parliament real powers (the panel tasked with writing the charter has been suspended amid bickering over its own Islamist-heavy composition).

"The changes in Israeli-Egyptian ties will be wide and deep," says Yoram Meital, chair of Middle East Studies at Ben-Gurion University in Beersheba. "Egypt is about to make a number of revisions to its security and foreign policies that many in Israel, particularly our decision makers, view with trepidation."

Mubarak's predecessor, Anwar Sadat, signed the Camp David Accords with Israel in 1978, followed a year later by a formal peace agreement -- the first ever by an Arab leader. The deal has never been popular among Egyptians (Sadat paid for it with his life), and in the presidential campaigns since Mubarak's ouster, Islamist and non-Islamist candidates alike have called for the treaty's revision or outright annulment.

Initial exit polls place the Muslim Brotherhood's Mohamed Morsi first, followed by former Prime Minister Ahmed Shafiq. Ex-Foreign Minister Amr Moussa, the former Brotherhood leader Abdel Moneim Aboul Fotouh, and the leftist nationalist Hamdeen Sabahi round out the top five. The top two candidates -- likely Morsi and either Shafiq or Moussa -- will go to a run-off vote next month, with the interim military rulers transferring power by July 1.

Israel officials most dread the prospect of an Islamist president. Aboul Fotouh regularly refers to Egypt's neighbor as the "Zionist entity," and the mainstream Brothers can themselves match any other Islamists for pure anti-Zionist and Judeophobic bombast. Morsi sat front row at a recent stadium rally as a preacher pledged the candidate would revive the Islamic caliphate, this time in Jerusalem: "Banish the sleep from the eyes of the Jews," chanted an MC, "Come on, you lovers of martyrdom, you are all Hamas!" (In Arabic it rhymes.)

In Egypt, however, opposition to the peace pact extends far beyond Islamists. Polls show 85 percent of Egyptians view Israel negatively, 97 percent see it as one of their country's biggest threats  and 61 percent want to overturn the treaty entirely (32 percent want to keep it; 7 percent are undecided). Anti-Israel sentiment cuts across class lines: Over the last year, opposition to the peace deal rose most sharply among the college-educated (up 18 points to 58 percent) and those under 30 (up 14 points to 64 percent). In Egypt's first-ever presidential debate this month, Aboul Fotouh described the Jewish state as an "enemy," while Moussa settled on the more diplomatic "adversary." (The latter has a decades-long record of anti-Israel bona fides; the anthem "I Hate Israel, I Love Amr Moussa" topped the Egyptian charts in 2001.)

Jerusalem has legitimate cause for concern -- of the five frontrunners, four have called for an overhaul of Camp David. Moussa has eulogized the peace accord as "dead and buried," Morsi urged it be put to referendum, Aboul Fotouh called it a "national security threat," and Sabahi warned that under his leadership, Egypt would no longer be Israel's "godfather" in the region. Shafiq, too, has begun burnishing his anti-Israel credentials: when an Islamist lawmaker recently accused him of Mubarak-era corruption, the former Air Force chief shot back that as a pilot in the 1960s he had downed two Israeli planes while the MP was still in his Nile cotton nappies.

In the 15 months since the start of the anti-Mubarak revolution, Egypt's political landscape has transformed, its economy entered a freefall, and tourism all but evaporated. The most dramatic change of all, however, has been the utter breakdown of government authority in the Sinai Peninsula separating mainland Egypt from Israel. There, local Bedouins run one of the world's briskest smuggling rackets: drugs and Libyan weapons to Gaza, Sudanese and Eritrean migrants to Israel (the prevalence of organ harvesting en route is one of the underreported stories of post-revolution Egypt). This month, the Knesset called up six reserve battalions and authorized an additional 16 amid ongoing instability on Israel's frontiers.

The breakdown in Sinai has already led to the shelving of the 2005 Egypt-Israel natural gas deal, a 15-year agreement whose terms many Egyptians viewed as too generous to Israel. The energy pipeline running through the peninsula has been sabotaged 14 times in as many months, and in April, the gas consortium's Egyptian partners severed the agreement outright, claiming their Israeli counterparts had welched on payment.

Armed extremists -- some linked to al Qaeda -- have also set up shop. Last summer, a dozen gunmen wearing Egyptian army uniforms waged a sophisticated multi-stage terror attack in southern Israel that left six civilians and two security personnel dead. The perpetrators -- most from Sinai, some from Gaza -- retreated to Egyptian territory, and in the ensuing chase Israeli forces killed 10 of the terrorists and, by mistake, five Egyptian troops.

Egypt demanded an apology; Israel refused. Weeks later, thousands of soccer hooligans ransacked the Israeli embassy in Cairo, prompting Jerusalem to recall all but one of its diplomatic staff home (footage later emerged of fans at a Cairo stadium raising the banner "One nation for a new Holocaust").

To many Egyptians, Camp David's most irksome terms are those stipulating the Sinai's demilitarization. The treaty allows Cairo to deploy only a single army division in the peninsula, the battleground for four Egyptian-Israeli wars over less than two decades. Closer to the frontier, only Egyptian police are allowed -- no troops. "It is a treaty that forbids Egypt from exercising full sovereignty," Aboul Fotouh said in the presidential debate. But Zvi Mazel, a former Israeli ambassador to Cairo, said altering the terms for Sinai troop deployments is not up for debate. "That's basis of the treaty," he said. "Without that, there's no peace."

Top-level Israeli security officials told me ties with their Egyptian equivalents remain largely unchanged since the Mubarak era. Still, further down the ranks, enmity boils: On a recent border tour with Israeli colleagues, more than one Egyptian policeman greeted us across the electrified fence with a one-finger salute.

"Sinai today is a powder keg. There is chaos there," said Benjamin Ben-Eliezer -- an Iraqi-born Labor Party lawmaker, ex-defense minister, and decades-long friend of Mubarak. Losing Egypt, he sighed, "will be a very big blow to us ... [We] must be prepared for the possibility of a confrontation."

I asked Prof. Meital of Ben-Gurion University if he thinks such fatalism is warranted. He said that while the last year's events do justify a certain apprehension, Israelis shouldn't let the doomsayers get the better of them just yet. "Much of Israel's public, and of course its decision makers, believe the Mubarak regime's fall has led to utter chaos. To me that's a simplistic understanding of the revolutionary transition that Egyptian society is undergoing," he said. "History shows such stages do lead at first to instability, but success must be judged with the perspective of years, not months. It's just a year after the regime's fall, after all, and free elections are already being held."

For many in Israel, nonetheless, the view across the border could hardly be bleaker. "It's hard to know whether we should talk about Egypt-Israel relations or the absence thereof," said former ambassador Mazel. "Whomever is elected president, the feeling is whatever comes next won't be good."

Note: this piece has been updated to reflect late-breaking exit polls from the presidential election on Thursday, May 24.