In his most aggressive attack yet on the Republican presidential nominee, Obama said Donald Trump was “unfit” to succeed him in the White House and called on Republicans to drop their support for him.

It is tempting to see in this categorical condemnation a necessary rebuke of Trumpism. Obama is acting as the mouthpiece of a broad coalition of public opinion, and condensing into its purest form what many of us already believe: Donald Trump is beyond the pale of acceptable, mainstream politics.

But as a deeply unpopular figure in Republican circles, Obama is also, intentionally or not, making it more difficult for Republicans to disown Trump. He may even harden the perception among Trump’s supporters that elite opinion is trying to delegitimize their supposedly anti-elitist candidate. Having already suggested that the November’s elections might be rigged to his disadvantage, Trump may find some ammunition in the president’s denunciation.