Background: the Lib Dems agreed to support the right wing agenda with their votes, in return for getting a national referendum on electoral reform. The referendum will (probably) take place on 5th May 2011 (the day of the Scottish and Welsh elections). The proposal is to replace First Past the Post with Alternative Vote (aka Instant Runoff or Preferential Ballot).
The problem for the Tories, as was obvious from the start, is that if the Lib Dems win the referendum they then have a strong motive to precipitate an election, in the hope of getting more MPs. The Tories have put in place various checks to prevent this happening, including setting the vote for precipitating an election too high for Lib Dems to reach. They are now also saying that even if the Lib Dems win the referendum the new voting method would not be introduced immediately. And now the Tory backbenchers are saying a change such as this requires a 'yes' vote from at least 40% of the electorate - a level of turnout which would be hard to achieve I think, particularly on a difficult technical issue like this (obviously the total turnout required would be way over 40%: up to 80% of the electorate would need to get out to vote).
There is also some talk of decoupling the date from the Scottish and Welsh elections (presumably to further reduce turnout) and this is where Straw has been unwise enough to offer an opinion. Just leave it alone, Jack.
(I'll post another time about how I think the referendum itself will play out - I think that depends on the result of the current framing).