I have been having a little play with one of my favourite web-based tools, the Electoral Calculus User-defined prediciton where you put in the voting percentages and it gives you the number of seats (based on a complex algorithm).
I put in the following scenario:
Have a look at what happens here. The Tories get 36% of the vote and Labour is 1% lower on 35%. I have put the Lib Dems in at a very low 17% (in order to make my point). Look at the number of seats. Labour would have 326 which is a small majority of 2, i.e. just over 50% of the seats. The Tories get less than 40% of the seats despite have won the popular vote!
Now the way things are looking at the moment this is very unlikely to happen, but let's hypothesise for a moment. Imagine that Brown is forced out late this year or early next year and Alan Johnson becomes PM. Imagine he then calls an election during a honeymoon period. Suddenly the Tory and Labour percentages above start to look less unlikely. I don't think the Lib Dems would do as badly as that but ironically in order for the argument for electoral reform to gain common currency we may need something like this to happen.
Imagine the newly elected Prime Minister Johnson trying to justify how he was going to govern for the next 5 years when he got less votes than the opposition and yet got more than 10 percentage points more seats. I think even some Tories would start to realise that things had to change at this point. That would be the perfect time for electoral reformers to make their case to the public as this scenario would perfectly illustrate the problem with First Past the Post.
It's all very well trying to argue about the difference between 35% of the votes and 55% of the seats (as the current Labour government got in the 2005 election) but because they did better than the Tories in the popular vote the unfairness gets lost. In the above scenario it would be abundantly clear that our electoral system is broken.
Like I say, it is unlikely to happen but you never know...