The Law and Policy Blog, David Allen Green: The moral hazard of the United Kingdom casually breaching the Political Declaration:

In effect: the Unite Kingdom is sending a signal of “don’t trust us, insist on strict legal obligations”. And this signal is not just being sent to European Union – the signal is now being broadcast to every nation in world, to all the countries where, post-Brexit, United Kingdom may want to have “trade agreements”. The United Kingdom may think it is saying to EU “screw you” but in fact it is telling the world “screw us”.

If this is political posturing in search of a better deal, I think they may have failed to think through the consequences.