Today's evidence: the banning of the country's two largest Arab parties from next month's(?) Knesset elections.
Now the ban on the Balad was probably long overdue, and it's a testament to the strength of Israeli democracy that Israel's semi-treasonous Arab nationalist bloc has been allowed to seat MKs at all. Israeli politics are such that the unseated Balad MKs probably could have been seated with another party--with the rival and more moderate United Arab List, or with a newly-formed right-wing Arab party untainted by the Bishara scandal.
The ban on the United Arab List is an ugly--albeit temporary--symptom of war hysteria. Chances are Balad and the UAL will both file suit in the country's Supreme Court, and chances are they'll both win (even Balad, whose lip-service to a two-state solution lets it sneak past the current ban on anti-Zionist parties in the Knesset, will likely be reinstated). Except that by a uniquely Israeli bureaucratic quirk, the committee that voted on the ban is actually headed by a Supreme Court justice. Worse, it's packed with MKs who might have a vested political interest in seeing the Arab parties dismissed: should the ban stand, the 7 MKs from Balad and UAL would have to run as down-ticket candidates with Hadash, Maki or another Arab-friendly left-wing party.
But it would take a dramatic, widespread change of heart for Israel's sizable bloc of moderate Arab nationalist voters to be suddenly drawn in by the Utopian and explicitly binational socialism of the Israeli left. Balad and UAL voters will probably stay home on election day, and remain disenfranchised, politically marginalized and deeply embittered--while right-wing parties that have capitalized on inter-communal distrust (Yisrael Beitanu comes to mind...) stand to pick up at least a couple of the vacated seats.
And if the ban isn't upheld, the parties whose CEC members voted for it (everyone but Labour, from the looks of it) will gain a short-term reputation for being tough on the Arab "fifth column" in the midst of a major conflict with the Palestinians. Successful or no, the attempt to ban the Arab parties turns racism into a not-so-subliminal electoral crutch (as if it wasn't already...)
A constitution that ensures free speech (or at least free speech within certain broad but acknowledged limits) and requires that elections be handled by a body other than the Knesset would prevent this kind anti-democratic posturing, as well as the procedural incoherency that allows it to take place--and it would reassure Balad and UAL voters that they have nothing to fear from their country's Jewish majority.