ISRAELI PRIME MINISTER Benjamin Netanyahu’s decision to call elections means that in January, as in 2009, a U.S. president will be inaugurated shortly ahead of a new Israeli government. Most likely that government will again be headed by Mr. Netanyahu, who starts his campaign with a commanding lead in the polls. The question will be whether President Obama or Mitt Romney will be able to use the fresh mandates in Washington and Jerusalem to launch a badly needed “reset” in U.S.-Israeli relations.

Though the Obama administration has worked closely with Israel in many areas, the president and Mr. Netanyahu have made a mess of their personal relationship. Mr. Obama sought to publicly distance himself from Israel early in his term, and he erred in centering his push for Israeli-Palestinian negotiations on a secondary issue — Israeli settlement-building in the West Bank and Jerusalem. He has never visited Israel. Mr. Netanyahu, for his part, publicly lectured Mr. Obama during his last White House visit, openly pressured Mr. Obama last month to set “red lines” on Iran’s nuclear program and made it relatively clear that he would welcome Mr. Romney’s election.

Mr. Netanyahu’s poor relations with Washington could cost him votes, particularly if Ehud Olmert, a centrist former prime minister, enters the race. But the incumbent will present himself to security-conscious Israelis as the best qualified to confront Iran. In a speech to the United Nations last month, Mr. Netanyahu suggested that Iran’s uranium processing could reach a critical point and invite a military strike by Israel by next spring or summer. If he wins the election, he might feel freer to ignore U.S. objections to such unilateral action, as well as those of Israel’s security establishment.

Mr. Romney has promised to eliminate the “daylight” between the U.S. and Israeli governments. But he, no less than Mr. Obama, will have to find a way to agree with Israel on a strategy for Iran that keeps with U.S., as well as Israeli, interests. Last week Mr. Romney told CNN’s Wolf Blitzer that he shared Mr. Netanyahu’s view that Iran should not be allowed to obtain the “capacity” to build a nuclear weapon — a stricter stance than Mr. Obama’s vow to prevent Tehran from building a bomb. But Mr. Romney added that “we have a long way to go before military action may be necessary” — a judgment that is closer to Mr. Obama’s than to the Israeli leader’s.

Neither Mr. Obama nor Mr. Romney is likely to succeed in policy toward Iran, not to mention their shared goal of creating a Palestinian state, unless they can forge a trusting relationship with Israel’s leader. Mr. Obama may hope that Mr. Netanyahu is unseated; perhaps Mr. Romney secretly shares that wish. But chances are that one of them will have to find a better way to do business with this prickly Israeli leader over the next four years than Mr. Obama has in his first term.