Not sure what you mean exactly Naomi. It's true that the Conservatives made said contract, containing a list of pledges by which the government was meant to be judged, and a message that failing to meet these targets meant that we should "vote [the Conservative party] out" if they had not met them. Well, the Conservatives haven't met many of those pledges, so... they've quietly dropped it in the, likely successful, hope that people will forget all about it.
The mistake the Conservatives made in 2010 was making a set of promises like this, an impossible standard if you will -- and Ed Miliband has now gone a step further by carving things he won't achieve in stone. Both sides are being berks about this sort of thing, which is the real point. You can't criticise Ed Miliband for this stupid stunt without acknowledging that the same sort of thing was done only five years before by the Tories.