If we vote for parties, then we should already have proportional representation as the constituency MP is irrelevant.
If we vote for MPs, then Chuka joining the Dems isn't much different to if Hoey joined UKIP. Doesn't change much.
I tried to think of an extreme analogy for this tweet, like the Republicans switching out George Bush for Trump immediately after Bush's election campaign victory... but switching out Theresa May for Boris Johnson is even MORE extreme!!
#BaitNSwitch
People voting for something on the basis of certain expectations and then the ruling party pretending those expectations don't exist so they can do whatever they like.