Roger Stone has a tattoo of Richard Nixon on his back. But it’s the current president, Donald Trump, who had Stone’s back when on Friday he granted a commutation of the 40-month sentence his friend was facing for lying during the Russian investigation.

In doing so Trump turned his back on the justice system and, ultimately, the American people by shamelessly shielding Stone, a felon convicted of obstruction of a congressional investigation, five counts of making false statements to Congress, and for intimidating a witness.

Even Attorney General William Barr, who often wrongly acts more like Trump’s personal attorney rather than the nation’s chief law enforcement officer, called Stone’s prosecution “righteous” and the final sentence “fair” (after working to reduce the length of it, that is).

Other, more principled Republicans were blunt about what can only be seen as a presidential protection racket. “Unprecedented, historic corruption: An American president commutes the sentence of a person convicted by a jury of lying to shield that very president,” Sen. Mitt Romney, R-Utah, tweeted on Saturday.

That description wasn’t far from what Stone said himself on Friday. “[Trump] knows I was under enormous pressure to turn on him,” Stone told journalist Howard Fineman. “It would have eased my situation considerably. But I didn’t.”

Another resolute Republican, Robert Mueller, who hearkens back to an era when “law and order” was a governing guidepost, not a Nixon or Trump campaign slogan, broke his long silence in a Washington Post commentary. The investigation, Mueller wrote, was of “paramount importance” because “Russia’s actions were a threat to America’s democracy.” Regarding Stone’s prosecution in particular, Mueller wrote that, “Stone became a central figure in our investigation for two key reasons: He communicated in 2016 with individuals known to us to be Russian intelligence officers, and he claimed advance knowledge of WikiLeaks’ release of [Clinton campaign] e-mails stolen by those Russian intelligence officers.”

So Stone’s crimes — and in fact, they remain crimes of which he is not absolved — were a direct threat to the electoral process, the DNA of our democracy. Criminals like Stone endanger justice itself. It was “critical,” Mueller wrote, for Congress and the Justice Department to obtain accurate information. “When a subject lies to investigators, it strikes at the core of government’s efforts to find the truth and hold wrongdoers accountable.”

Mueller’s patient, painstaking explanation contrasts starkly with Trump’s claim that Stone was treated “very unfairly.” On the contrary, it’s Americans who were treated unfairly by Stone, and by a president buying his silence.

Every president has broad prerogative on clemency and pardons, and the congressional calls for reform must pass constitutional muster. Trump is not the first to make controversial calls on these matters.

But few, if any, uses of presidential powers have been as egregious as this.