The South Carolina Republican senator Lindsey Graham called Joe Biden after his victory over Donald Trump to tell the president he only joined attacks on his son, Hunter Biden, as a “bare minimum” to satisfy Trump supporters.

The detail was included in a lengthy profile of Graham and his Washington manoeuvres published by the New York Times. It said the call, intended to “revive a friendship damaged by [Graham’s] call for a special prosecutor to investigate the overseas business dealings” of Hunter Biden, was “short, and not especially sweet”.

Hunter Biden’s brother, Beau Biden, died in 2015. Their sister Naomi was killed with their mother, Neilia Biden, in a car crash in 1972. Biden has a daughter, Ashley Biden, with his second wife, Jill Biden.

Hunter Biden’s business dealings in Ukraine were at the heart of attempts by Trump allies to find dirt on Joe Biden as the 2020 election approached. Trump was impeached over the issue. Graham joined other Republicans in rallying behind their leader. Only one GOP senator, Mitt Romney of Utah, voted to convict, on a charge of abuse of power.

Hunter Biden’s business and personal life was then at the centre of attempts to influence the election with an “October surprise” – which fell flat. He has since released a memoir and remained the subject of controversy over what his dealings may mean regarding presidential ethics.

Graham was a longtime friend and ally of John McCain, the 2008 Republican presidential nominee who, like Biden, was an influential voice on foreign affairs while in the Senate.

McCain opposed Trump’s takeover of the Republican party. So initially did Graham, who in 2015, while running against Trump for the presidential nomination, famously called him “a race-baiting, xenophobic bigot” who “doesn’t represent my party”.

Once Trump did represent the Republican party as its nominee for president, Graham executed what the former Clinton aide turned historian Sidney Blumenthal has called a “reverse ferret”, to become one of Trump’s most fervent supporters and frequent golf partner.

But Graham did so as a long-term friend of Biden, once saying: “If you can’t admire Joe Biden as a person, then you got a problem. You need to do some self-evaluation. ’Cause what’s not to like?”

To the Bidens, returning Graham’s gaze, it seems the answer is now “quite a lot”.

In February the first lady told CNN: “I don’t know what happened to Lindsey. We used to be great friends. I mean, we traveled together with the [Senate] foreign relations committee, we had dinner, you know … And now he’s changed.”

The Times said Graham made his call to Biden in November, even while he actively supported Trump’s attempts to overturn his defeat, himself ending up under investigation for a call to an election official in Georgia.

Citing two anonymous sources close to the president, the Times said that shortly after the call, Biden said: “Lindsey’s been a personal disappointment, because I was a personal friend of his.”