The Lib-Dems were victims of the ludicrous first-past-the-post system, again. Principles are all very well, but it is a FACT that if you live in a constituency with an intransigent, herd mentality (ie. MOST constituencies), a vote for anyone other than the incumbent party is a wasted vote.
Our system appears to be rooted in the days when the (few, male, influential) voters in a village elected a local chap (Tory or Whig) to go and vote on their behalf down in 'that London' and news would occasionally filter back to the town.
In recent decades the traditional working class voted for Labour and 'posh' people for the Tories. New-Labour kept the old voters (because the word "Labour" was still on the ballot?) , but also sucked-in many of the Thatcher fans.
Nowadays we can email the Prime Minister, conduct an internet campaign, get onto TV news etc. I don't really value my local MP as the city council are responsible for much of the 'local' issues, not a bloke who sits in Westminster towing the party line.