His administration has spent the weeks since the fall of Baghdad in a slow but deliberate retreat as the goalposts on why the US launched a pre-emptive strike on Iraq haven't just moved - they've positively revolved.
The President's presumption of mass destruction - that coalition forces would be tripping over weapons of mass destruction after defeating Saddam Hussein's troops - has proved wrong.
The justification for a pre-emptive strike was that Saddam had failed to co-operate with inspectors, therefore he was concealing these illegal weapons.
Now Bush aides are pushing a new line - confirmed by Donald Rumsfeld's astonishing declaration yesterday -that Saddam may have destroyed the WMD as demanded by the UN after all.
Instead of looking for banned materials, it is now pinning its hopes on finding documentary evidence.