Donald Trump has reached a position of such demagogic lying that no truth will be able to bring him and his campaign back to the realms of sanity. And the alarming fact is that his supporters will stay with him all the way.
In any rational political campaign Trump should have been finished when he slandered a judge on the grounds of his ethnicity. The case awaiting that judge's ruling - over the failure of Trump University to adhere to its published prospectus - should also have rebounded firmly against Trump. This man who parades himself as the saviour of white American working class citizens wilfully conned many of them out of hard earned savings with the false promise of riches through his "university" set-up. And yet he went on to seize the Republican nomination and runs Hillary close enough in polls to suggest he may well win in November.
Trump's racism and bizarre political headline - to build a wall along the Mexico border - should also have holed him beneath the waterline as a dangerously divisive populist and a spewer of fantasy politics. It has done no such thing.
Trump's aggressive misogyny towards a Fox News reporter early in the primary campaign should have ruined him irreparably, but he continued to push forward against an anaemic and spineless group of "opponents".
Then came Trump's call on Russia to hack into Hillary's emails. His willingness to engage the support of a hostile foreign power, and essentially underwrite their own malign interference in America's election campaign, should have made him a pariah, and yet his continued vocal support for one of the world's most corrupt and power-hungry despots, Vladimir Putin, somehow makes good waves for him amongst his legion of supporters.
This week alone Trump has endured - and will survive - his ill-judged criticism of a mother who lost her son in an heroic action against the very Islamic terrorism that Trump claims to defy. Trump - the man who profited from buildings while others sacrificed their lives in war - is immune to any of the normal standards of decency that might apply in a political fight, and certainly to the higher standards that apply in everyday life. He calls Hilary Clinton the "devil" (and means it), encourages chants of "lock her up", and spits out venom every time he speaks or tweets. He now claims that the election will be rigged against him. He is, to all intents and purposes, a malign man who is completely out of control.
And yet he could be president. His supporters have remained tight and his party - with a few individual exceptions - refuse to disassociate themselves from him. We have come to expect men of the calibre of House Republican Speaker Paul Ryan to avert their gaze from Trump on an almost daily basis and keep supporting him. Ryan long ago lost his backbone in this struggle, and stands condemned as Trump's fellow traveller no matter how awkward he may occasionally seem to be.
But the real sign of alarm for America is how Trump's campaign has infected and is destroying a land once hailed for its openness and freedom. His attack on a Muslim military mother for staying silent during a convention appearance should have breached the last wall. It almost looked as if it had with Republicans like John McCain and Jeb Bush rounding on him. But they are mavericks or has-beens and out of the loop. It's the Trump supporters who bear attention, and they have rallied around him.
Take this story of another military mother who dared to ask an adverse question of Trump's vice-presidential candidate Mike Pence. As soon as she even suggested that Trump had dis-respected the military, the Trump supporters at the meeting booed her, harassed her and tried to drown her out. Afterwards, it was she - not Mike Pence, the vice-presidential candidate serving as an empty vessel for Trump's extremities - who received criticism from the crowd members.
Think on that. Think on the spectacle of an America so utterly subverted that a manipulative, congenitally deceitful businessman whose career has been spent exploiting others, should be seen as somehow more honourable and moral than a mother seeking to defend respect for military heroes.
It is only as that sinks in that you realise the enormity of what is happening in America. It is a democracy, and it changes not just because of one man but because ordinary people change it. Trump has already won the votes of over 13 million Republicans. Despite everything he has said, despite his career history, his refusal to be honest with his tax returns, his frequent and scatter-gun abuse and his friendliness towards America's foreign enemies, this man retains the support of a huge swathe of American voters. Whether he wins or loses in November - and he has a high chance of winning - America has already changed. He hasn't changed it. But he has channeled the hate, bigotry and division of so many Americans that the fabled shining city on a hill really is no more.