Let me try to summarise the British electorate in a schematic model.
Hang on, it's not quite that simple. Try this...
That's a core group of people who always vote Labour, a core group of people who always vote Conservative, and then everybody else in the grey bit.
The grey bit's important, because it's the grey bit that decides elections. Forget the red bit and the blue bit, because no campaign ever persuades these people to change their minds. They're set in their ways. They'd vote for a monkey if you stuck the appropriate coloured rosette on it. Oh no, the outcome of any election is dependent solely on the undecideds and 'others' in the centre. Persuade enough of them over to the left and we get a Labour government, whereas if the blue magnet is stronger we get Tory rule.
Me, I'm in one of the two end sections. I always know how I'm going to vote before any election is called. The campaign has no effect on me, so instead I spend four weeks watching fascinated as the grey folk in the middle make up their minds. Bunch of impressionable ditherers, many of them, unable to choose one way or the other until swung by a reasonably good speech or a biased newspaper headline. It's the people with the shallowest convictions who decide elections, and not always for the best of reasons.
Usually enough of the grey folk move decisively to ensure that Britain gets a majority government. Usually there's enough momentum to left or to right, and the country ends up locking into red or blue for four or five years. But the system doesn't always work like that, because there are additional tempting choices in the centre. Here's a better model.
The yellow option occupies an increasingly important chunk of the political middleground. No longer are greys forced to decide between red or blue, not now there's a serious third influence to consider. Which way to jump? Decisions decisions decisions.
And there's an additional complication. In a voting system where proportional representation isn't the norm, many electors are going to choose to vote tactically. Sometimes the important thing isn't who to vote for, but who to vote against. Because in reality the red end isn't pure red, it's a group of people who'll never vote blue. Likewise the blue end isn't true blue, it's a group of people who'll never vote red. Anything to keep the other lot out, whoever the 'other lot' might be. Does that sound more familiar?
not red not blue
So in a mould-breaking election where neither extreme has the momentum, what Britain may end up with is a 'Not' parliament.
A Lib/Con coalition that's very definitely Not Red.
Or a Lab/Lib coalition that's very definitely Not Blue.
And you never know, more of us may even prefer it that way.