The first-past-the-post voting system that we use for Parliamentary elections works very well if there are only two main parties. Most voters select one or other, and a handful exercise their right to support tiny minority parties. The party with the most seats will almost certainly, in this case, represent the majority of voters in the country.
But the UK has not been a two party state for some time now. Over the last 30 years or so, Liberal Democrats have been gradually increasing their share of the vote, up to around 20%-24%. In Scotland and Wales, the SNP and Plaid Cymru are serious contenders as well.
The voting system is no longer fit for purpose. The recent growth of support for the Liberal Democrats has shown this only too well.
The Observer yesterday looked at some possible outcomes of the election, starting with the case where Conservative, Labour and Liberal Democrats all gain 30% of the popular vote, with the remaining 10% given to others.
Although each party would be equally popular, Conservative would gain 206 seats, Labour 315 seats (almost an outright majority) and Liberal Democrats 100 seats.
This bizarre outcome is because Labour and Conservative have each consolidated their position in a large number of safe seats in geographically distinct areas. In contrast, support for the Liberal Democrats is spread widely across all parts of the country.
How about this outcome, which is roughly in line with some of the opinion polls: Conservative 33%, Lib Dem 30% and Labour 27%. What then?
Unbelievably, although lowest in popularity, Labour would gain the most seats with 262. The Conservatives would come second with 257. Faced with that result I can't imagine that the Tories would still uphold their opposition to electoral reform.
And where would the Lib Dems be? They would get exactly 102 seats.
So, although the Tories would beat Lib Dems by 3% they would get 155 more seats.
As The Observer comments: "Beyond parody"
Electoral reform - or fair votes - is essential if democracy is to survive in a three sided contest. That is why electoral reform is the unwavering requirement that Liberal Democrats would take into any post-election negotiations.
David Cameron was still saying today that first-past-the-post serves the country well.
No, it doesn't. But this time the voters are far more aware of the unfairness than ever before. If, after the election, the outcome is similar to either of those that I have quoted, then the voters will simply not accept the unrepresentative result in Westminster.