I agree that this phenomena exists, but along with others.
For example, yellow may gain control, and try to aggressively implement their more extreme policies. This causes purple to move further divergent, and a majority are attracted to that.
I agree that there are certainly other phenomena, one of which is similar to the position you outline.
A consequence of the parties moving towards the centre, and becoming more similar to one another is that many voters start to feel that they have no real choice other than voting to perpetuate the status quo, and that neither of the mainstream candidates represent them. This causes people to move away from politics altogether, and creates an army of available potential voters... a huge power just waiting to be harnessed. This I think is why in recent years, after we've had the move to the centre, we are now seeing the rise of more extreme candidates from both left and right, anti-establishment outsiders (and people posing as such) who rail against the system and promise to create something different and better.
We have seen the election of right-wing populists in quite a few countries around the globe, but the left-wing populists for the most part remain out of power. A couple of reasons for this I think are:
a) The mainstream media are controlled by millionaire/billionaire individuals who for personal reasons will always favour a right-wing leader, and so go out of their way to demonise any left-wing alternative, and the more left-wing the contender, the more extreme and vitriolic the media aggression.
b) Left-wing populism is more abstract and tends to appeal more to theorists, restructuring tax brackets, renationalising previously privatised utilities, etc... whereas right-wing populism is more in-your-face everyday stuff: keep the immigrants out, don't pay poor people to sit around and do nothing, etc. Right-wing populism is aggressively oppositional, and stokes the fires of resentment, which is a powerful motivator.
