Well.... the recent polls have given the impression to many that the anti-status quo forces will finally get a chance to -let's say- make an impact on policy by having greater representation.
An outcome which would relegate them (once more) into irrelevancy might not be so readily accepted as the "true will" of the people and all that will be needed to transform their justified indignation from protests to outright violence would be for ex. accusations of fraud or other conspiracy theories which are much more believable in the current Greek political context.

The electoral law is rigged and nobody disputes that. All it takes, is for 10% of the vote to be wasted on parties that never had a chance to gain 1 seat and other small parties currently polling at 3%-5% not making it afterall. PASOK (my opinion) will probably go as high as 15%-18% which will lead to a centrist govnt lead by.... the Troika/IMF candidate, Papademos.