A loving act of mercy by a father who has already known much sorrow? Or a hypocritical political manoeuvre reminiscent of his great foe? Maybe both can be true.

Joe Biden’s announcement on Sunday that he had pardoned his son Hunter, who is facing sentencing in two criminal cases, is likely to have been the product of a Shakespearean struggle between head and heart.

On the one hand, Biden is one of the last great institutionalists in Washington. “From the day I took office, I said I would not interfere with the Justice Department’s decision-making,” he said in an unusually direct and personal statement on Sunday. To undermine the separation of powers goes against every fibre of his political being.

On the other hand, Biden is nothing without family. His speeches are peppered with references to his parents. As a senator, he once took a train from Washington to Wilmington, Delaware, so he could blow out the candles on a birthday cake for his eight-year-old daughter, Ashley, at the station, then cross the platform and take the next train back to work.

Biden was profoundly shaped by the death of his first wife, Neilia Hunter Biden, and 13-month-old daughter Naomi in a car accident and, much later, the death of his son Beau from brain cancer. In that context, Hunter’s status as the first child of a sitting president to face criminal charges will have pained his father in what Ernest Hemingway called “the broken places”.

Hunter was convicted this summer of lying about his drug use when he bought a gun. Joe Biden categorically ruled out a pardon or commutation for his son, telling reporters: “I abide by the jury decision. I will do that and I will not pardon him.” Hunter also pleaded guilty in a separate tax evasion trial and was due to be sentenced in both cases later this month.

Biden reportedly spent months agonising over what to do. The scales were almost certainly tilted by Donald Trump’s victory in last month’s presidential election. The prospect of leaving Hunter to the tender mercies of Trump’s sure-to-be politicised, retribution-driven justice department was too much to bear. Biden typically takes advice from close family and is likely to have reached the decision after talking it over during what was an intimate Thanksgiving weekend.

“No reasonable person who looks at the facts of Hunter’s cases can reach any other conclusion than Hunter was singled out only because he is my son – and that is wrong,” the president said in a statement, calling it “a miscarriage of justice”.

He added: “There has been an effort to break Hunter – who has been five and a half years sober, even in the face of unrelenting attacks and selective prosecution. In trying to break Hunter, they’ve tried to break me – and there’s no reason to believe it will stop here. Enough is enough.”

Joe Biden’s defenders will certainly contend that, if Hunter had been an ordinary citizen, the gun case would not have come this far, and his father was simply righting that wrong. Republicans spent years hyping investigations into Hunter that failed to produce a shred of evidence linking his father to corruption.

Eric Holder, a former attorney general, wrote on social media that no US attorney “would have charged this case given the underlying facts. After a five-year investigation the facts as discovered only made that clear. Had his name been Joe Smith the resolution would have been – fundamentally and more fairly – a declination. Pardon warranted.”

It was also noted that this is hardly the first time pardons have smacked of nepotism. Bill Clinton as president pardoned his half-brother for old cocaine charges, and Trump pardoned the father of Jared Kushner, his son-in-law, for tax evasion and retaliating against a cooperating witness, though in both cases those men had already served their prison terms. Trump also used the dog days of his first presidency to pardon the rogues’ gallery of Steve Bannon, Michael Flynn, Paul Manafort and Roger Stone.

And yet for many Americans there will be something jarring about the double standard of a president pardoning a member of his own family ahead of numerous other worthy cases. Republicans in the House of Representatives naturally pounced with more hyperbole about the “Biden crime family”.

But there were also more thoughtful objections. Jared Polis, the Democratic governor of Colorado, wrote on social media: “While as a father I certainly understand President Joe Biden’s natural desire to help his son by pardoning him, I am disappointed that he put his family ahead of the country. This is a bad precedent that could be abused by later Presidents and will sadly tarnish his reputation.”

Joe Walsh, a former Republican congressman turned Trump critic, said on the MSNBC network: “Joe Biden repeatedly said he wouldn’t do this so he repeatedly lied. This just furthers cynicism that people have about politics and that cynicism strengthens Trump because Trump can say, ‘I’m not a unique threat. Everybody does this. If I do something for my kid, my son-in-law, whatever, look, Joe Biden does the same thing.’ I get it but this was a selfish move by Biden, which politically only strengthens Trump. It’s just deflating.”

The Trump context is impossible to ignore in this moral maze. Next month he will become the first convicted criminal sworn in as president, though three cases against him have all but perished. He is already moving to appoint loyalists to the FBI and justice department.

Michelle Obama once advised, when they go low, we go high. On Sunday Joe Biden, 82 and heading for the exit with little to lose, decided to go low. Perhaps it was what any parent would have done.