Recent polls had indicated if Shelly Yachimovich prevailed in the Israeli Labor party’s internal leadership elections, the party would make a strong comeback. Yachimovich did, and the polls have held steady. Haaretz gleefully proclaims the “Shelly Yachimovich Effect.” And it might be real.

The poll, however, doesn’t contain any bad news for Benjamin Netanyahu and the Likud party. Netanyahu’s popularity seems to have received a boost from his eloquent, tough speech to the United Nations General Assembly late last week. And Avigdor Lieberman’s Yisrael Beiteinu party is due to continue gaining seats in the Knesset, as previous polls have shown. So who loses enough seats to allow Labor to triple its Knesset representation (and allow left-wing Meretz to gain a couple)? Tzipi Livni’s Kadima:

Kadima is bleeding Knesset seats not only to Labor, but also to Meretz, which was in no way hurt by Yachimovich’s election. In fact, a survey by Haaretz shows Meretz gaining two Knesset seats after the Labor vote.

Yachimovich seems to be on her way to keeping the promise she made to voters on the night she was elected to transform Labor into a party larger than Kadima.

There are a host of predictable reasons for this. Kadima was founded by Ariel Sharon to carry out the 2005 disengagement from Gaza and parts of the West Bank. The disengagement itself went mostly as planned. But the government completely bungled the relocation of the settlers and its response to the creation of “Hamastan” and the ensuing violence.

After Sharon’s illness incapacitated him, Ehud Olmert took over. Plagued by corruption, the mismanagement of a war with Hezbollah, and a general appearance of weakness, Kadima was promptly removed from power in the next election. It is widely viewed as lacking both ideas and the ability to govern.

To make matters worse, Livni, though somewhat well-liked by the public (and the Obama administration), has offered only tetchy, self-conscious, lethargic party leadership. Unsurprisingly, Netanyahu has run circles around her. And there is another development Haaretz calls attention to:

The poll reflects a major change in the makeup of the Knesset: Instead of the usual two large parties, there will now be four medium-to-large parties with not much difference between them.

I discussed this trend, and predicted it would continue, in our July issue. The fragmentation of Israeli party politics is a phenomenon that may very well become the new normal. In such a situation, Kadima could survive, but would almost certainly be marginalized.

The lure of centrist parties is often a mirage. Voters love to tell pollsters they are “centrist,” but that is usually because most voters consider their opinions to be mainstream and reasonable. If Israelis are offered a serious center-right party (Likud), a serious center-left party (Labor), a serious secular nationalist party (Yisrael Beiteinu), and a couple of religiously or ideologically homogeneous parties (Shas, Meretz), Kadima’s appeal will be quite limited.

Livni may look back with regret on her decision to reject Netanyahu’s offer to join his government. Her career may be the first major political casualty of the Shelly Yachimovich Effect.