Among those who work for him, former FBI director James Comey is known as a very straightforward man who absolutely detests bullies.
It is clear that he decided long ago that Donald Trump is a bully.
Extracts from his new book ooze contempt for the commander-in-chief, and the interviews he is giving are even worse.
There's the forensic recounting of their meetings in which, among other things, he says Trump requested loyalty and pressed him to drop an investigation into disgraced former national security adviser Michael Flynn.
There's the damaging conclusions that a professional measurer-of-men has come to; that the President is "untethered to the truth" and unfit to serve.
On the face of it then, Comey's book should pose quite a threat to the reputation of a President still embroiled in the Russia investigation, and scandals involving women allegedly paid off to keep quiet about affairs.
::Trump 'morally unfit' to be President, says fired FBI boss James Comey
But I don't think it's going to have the kind of effect Comey perhaps imagined it would.
To start with, Comey has strayed too far into barely concealed hatred and mockery, commenting on Trump's hair, skin tone, hand size and so on.
In this way he has joined Trump – who tweeted that Comey was a "slimeball" – in the sandpit with all the other toddlers, and rather detracts from the impact of his other assertions.
:: Fired FBI boss Comey talks Trump: Key moments from his tell-all interview
The tone of his interviews will help the White House to frame Comey as a disgruntled ex-employee out for revenge.
They might be right.
Separately, the optics of one of the most powerful former law enforcement officials in the country swinging for Trump may also give the President and his supporters more ammunition when they argue that the establishment, or the state, is somehow out to get him.
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Comey clearly has a sense of himself as a man – as the title of his book suggests – with a higher purpose.
But if the book itself is anything like the leaked extracts and his interviews, he may have fallen short on this mission.
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