Why can't the Israeli Left seem to revive itself ?

[Oryxslayer]

Depends entirely on how you define Left. The types of voters who put Labor or Labor-type parties into power until recent decades are still there, and still voting for parties many would consider on the Left. In fact like most countries things like this are 50-50 in the past few years many elections, though recent court fights and conflicts have broken things in their favor.

Now if you define things in the far, far, unhelpfully narrow sense then you have to look at the history, cause in multi-party systems voters will just find more viable tickets if one is in trouble.

The first issue is that Labor-like parties started as the dominant party in Israel, but presiding over a multiparty system. PR systems around the world started as a 2 or 3 party system and over time smaller parties have multiplied off increasing voter information and weaking party connections. This created more parties in the "lane" of voters once occupied by Labor.

Secondly, Labor, like many multiparty European Soc-Dem/labor parties, is a old/'pensioner' party. The old people with memories and a history of party connections  stick by them even in the bad times. But newer voter groups don't have that history, and since this is a multiparty system, they move to other more viable tickets. And parties follow their voters, which could/did send voters to other parties in their Lane.

With all that said, the recent History of Labor was a struggle with these two factors. Declining vote share but a traditionally dominant role put them as members of coalitions against certain parts of their values. Which pushed more people away, more old people died, and the vicious cycle almost consumed them. Then Labor was more or less saved by the election repetition process of a few years ago. The polarization meant voters didn't want to see their 'block' fail, and loaned votes. Which providing breathing space for Labor to reorient into something more younger, more activist, more happy to team up with the Greens.