Given: Israel cannot live with repeated bouts of missile fire from Gaza aimed at normal people living everyday lives. This is the description of an unbearable problem—but not a reason to believe that the problem can be quickly cured, or that the cure is massive military force.

As of Wednesday morning the latest bout—like ones before it—had ended in a fragile ceasefire, reportedly brokered by Egypt. So why did Prime Minister Netanyahu and Defense Minister Barak decide this was the time to assassinate Hamas's military chief, begin a bombing campaign, and prepare a possible ground invasion?

Two partial answers whisper from between the lines of news reports. Both can be true at the same time. The first is that the IDF's generals knew where to find Hamas's Ahmed Jaabari and the organization's missile supplies, and had developed a contigency plan to use that information to weaken Hamas militarily. Now there was a reason to use it. This is an old Israeli story: Generals have a tactical answer and persuade politicians that it is a strategic solution. Afterward comes a desperate diplomatic effort. Reversing Von Clausewitz's adage, policy becomes an extension of war.

The second answer is political: An election is two months away. Ehud Barak's party isn't expected to get enough votes to return him to the Knesset, and Netanyahu sees slippage in the polls. Between naiveté that denies that an Israeli leader could ever let electoral considerations affect his military choices and cynicism that says leaders will use any means to stay in power, there is a realistic, ambiguous middle ground: Politicians may not consciously risk lives on both sides of the conflict for votes. But elections can shade the judgment of elected officials, sometimes badly.

Israeli history is rich with case studies. In early October 1973, campaign ads of the ruling Labor Party declared, "On the banks of the Suez, all is quiet." Defense Minister Moshe Dayan was the living symbol of Labor's claim that it had prevented war. Early on Yom Kippur, the final, definite intelligence report warned that Egypt and Syria were about to attack. But Dayan still wanted to believe war was a lesser risk than panicking the country with a false alarm, and resisted a full call-up of the reserves. Worried about domestic perceptions, he left Israel far weaker when the attack came.

Jump forward eight years. Before the 1981 elections, Prime Minister Menachem Begin ordered the bombing of Iran's Osirak reactor. Leave aside the debate over whether destroying Osirak slowed or accelerated Iraq's nuclear program, or whether the raid itself was a political ploy. Begin's announcement (pay wall) of Israel's responsibility was certainly aimed at voters. Iraq had yet to acknowledge the attack, and until Begin spoke, Iran was the more likely suspect. The announcement caused Israel absolutely unnecessary diplomatic damage, but helped Begin win a narrow victory over Labor's Shimon Peres. Before feeling too sorry for Peres, remember his own gambit as prime minister in the spring of 1996: the Operation Grapes of Wrath offensive in Lebanon was widely seen at the time as a pre-election bid to boost Peres's security credentials. If anything, it had the opposite effect, contributing to yet another narrow defeat for Peres.

For the past four years, Netanyahu and Barak have pushed the Palestinian issue off the Israeli political agenda—and demonstrated their toughness to voters—through constant threats to attack Iran. The reelection of Barak Obama, rumors of impending U.S.-Iran negotiations, and the report that Netanyahu and Barak came close to ordering an attack in 2010 without cabinet approval all have made it harder for them to make Iran their campaign issue. Meanwhile, a restrained response to missile fire in the south it is harder to explain with elections two months away.

The best-planned wars don't go according to plans, so no one knows how this operation will end. If Egypt manages to arrange another ceasefire, the silver lining will have a cloud: Netanyahu will say that force worked. Forgetting the brief ceasefire that preceded the offensive, many voters will believe him. If the fighting continues, relations with the new regime in Egypt could get far worse. The Israeli right will use that as evidence that peace treaties aren't to be trusted.

The initial response of the Israeli public when the IDF is ordered into a major offensive is to rally around the government, to see the action as essential. Later, after the deaths on both sides, after an ambiguous resolution, neither victory nor defeat, a political hangover often sets in. If regret comes this time, no one knows whether it will take less than two months or more. Meanwhile, the unbearable problem in the south may recede—until the next bout.