"Absolutely sure" that Trump is currently conducting an affair, though "he has no proof". But it's in his book, so it must be true, at least to TDS sufferers.
These are not the days of Democrat hero JFK, when an adoring press was only too glad to cover up his affairs with Hollywood starlets and anyone else who could be charmed out of her (his? Don't want to appear trasnsgender phobic here) dress. 60 years after Kennedy, a huge contingent of Secret Service agents, even more aides and flunkies, and a swarm of reporters follow Trump wherever he goes. Bill Clinton received his blowjobs in the Oval Office and (almost) got away with it, but like Kennedy, he had a Democrat press to help hide his proclivities; Trump has no such allies.
In short, Wolff's absurd claim is as false as his other inventions, but for Trump haters, who require a new daily fix of allegations to replace the one they lost the day before (in just the past five days, he's been described as psychotic, senile, and about to die from a heart attack), any lie in a storm will do.
The Wikipedia bio of Wolff has this to say about his credibility::
In the fall of 1998, Wolff published a book, Burn Rate, which recounted the details of the financing, positioning, personalities, and ultimate breakdown of Wolff's start-up Internet company, Wolff New Media. The book became a bestseller. In its review of Wolff's book Burn Rate, Brill's Content criticized Wolff for "apparent factual errors" and said that 13 people, including subjects he mentioned, complained that Wolff had "invented or changed quotes".
"Well that was twenty years ago", Wolff told FWIW. "I'm a changed man, believe me".