Should the Tories really be worried by electoral reform? The idea of a "progressive majority" that enthuses many on the left rests on the assumption that people will continue to vote as they do if the system is changed. Not all Liberal Democrat voters are particularly left wing, many are basically centrist. Most countries with PR do not continually elect left wing governments.
Besides as both Michael Portillo and Simon Heffer point out today, electoral reform maybe something which is inevitable, so it is therefore a question of whether it is done in a manner designed to bolster the Labour Party's grip on power or not.
Given the tribal antipathy towards the Tories in many parts of the country it is possible that it could open up the possibility of a new force on the right that can appeal to groups who are set against them.
It could even be a really good means of stuffing the Labour Party, If they offered the Lib Dems a deal of AV+, with redrawn constituencies to neutralise Labour's inbuilt advantage of smaller electorates, and some restrictions on Union funding then they could finish Labour off.