My MP Steve Baker has linked to this video, to explain why all politicians end up saying the same thing:
I've commented there to explain that while this is a persuasive theory, and explained well, it makes one significant assumption that is not borne out in practice. It assumes that the views of the voters are a given, that they are fixed and inflexible. The task, then, of the politician is to tailor his or her views so as to maximise his or her vote.
This is of course a very cynical approach to politics, which entails the candidate deceiving the electorate and espousing a set of views that s/he does not hold and does not support. Some might say that was not the best start to a political career (although others might disagree). More seriously, however, it is a flawed assumption. Voters do change their mind in response to what they see happen and what they hear via the media channels that are fed to them.
So let us postulate a country with a two-party system in which one party pursues the approach set out in the video, and the other actively seeks to control the media agenda and use it to present a viewpoint favourable to it. What will happen? Well, there will be a gradual shift of the views of a large part of the population towards the latter party, let us call them the "Manipulative Party". By their consistent presentation through the media of an agenda suited to their beliefs, they create a climate of public opinion that matches theirs, and control the terms of debate and its language so that the voter population are not just persuaded by the outcome, they begin to think along the lines dictated by the Manipulative Party.
Meanwhile, the other party, let us call them the Responsive Party, note this shift in public debate and respond to it by tailoring their message in the same manner, forever chasing the movement of the voter population towards the Manipulative Party. The result: as before, both parties say the same thing - but that thing is the message of the Manipulative Party.
Meanwhile, what happens to the voters who hold the views originally espoused by the Responsive Party? They are left over at the other end of the see-saw, abandoned. They drift away, disillusioned and disappointed. But the Responsive Party picks up more voters than it loses, right? Wrong - the voters it is nearest to can see full well that it is trying to put out a message that it has never held, and which it is only putting out in order to chase votes. So it fails to gain their trust, and loses out overall.
The result is sadly predictable - the Manipulative Party spins its way to victory while the Responsive Party loses the argument every time. The only chance of power for the Responsive Party is when the policies of the Manipulative Party have their inevitable catastrophic effect and the Responsive Party gain power (perhaps in a coalition?) briefly in order to patch things up.
It will come as no surprise if I say how I think this analysis applies to British politics. So I won't bother.