For months, Donald Trump had made outrageous statements.
It has been his tradecraft. Coded race references, playing to conspiracy theorists, polarising opinion. That has been the basis of his Presidential campaign.
But has he now gone so far out of the mainstream - towards fascism, according to his opponents - that his campaign is about to implode?
Last night, at a rally in South Carolina, he demanded that America ban all Muslims from entering the United States.
But his voice is not alone. He is echoing what is being said in many homes across the country. Suspicion and distrust of America's Muslim population is stronger that I have ever seen.
That is no surprise in the aftermath of the California massacre.
But the danger is not just the hugely offensive and immoral nature of the rhetoric from Trump.
It also serves the ISIS narrative.
The group's leaders can now take perverse pleasure in the fierce over-reaction.
They can believe they are just a few terrorist attacks from creating a backlash that might lead to the clash of civilisations that they yearn for.