More than 400 former federal prosecutors have signed a new letter claiming that President Donald Trump’s interference in the Russia investigation, as described by special counsel Robert Mueller’s report, should have led to “multiple felony charges for obstruction of justice.”

The letter, circulated by the anti-Trump group Protect Democracy and first reported on by the Washington Post’s Matt Zapotosky, is pretty brutal. According to the former Justice Department officials, Trump’s actions as detailed by the Mueller report, which ranged from interference with Mueller’s attempts to acquire cooperating witnesses to an attempt to fire Mueller, constitute severe inference with the federal inquiry. In fact, they say, the question of whether there’s enough evidence to charge Trump isn’t even a particularly tough call.

“All of this conduct — trying to control and impede the investigation against the President by leveraging his authority over others — is similar to conduct we have seen charged against other public officials and people in powerful positions,” the letter’s text says.

“To look at these facts and say that a prosecutor could not probably sustain a conviction for obstruction of justice — the standard set out in Principles of Federal Prosecution — runs counter to logic and our experience.”

The only reason Mueller didn’t indict, they believe, is that Trump is “covered by the Office of Legal Counsel policy against indicting a sitting President” — something Mueller believed it would be above his pay grade to contradict. Instead, he reserved judgment on whether Trump should be indicted and asked Attorney General William Barr to make the final call on the matter.

The problem, though, is that Barr is hardly a trustworthy party.

Before his appointment as attorney general, he wrote a secret memo to the White House bashing the legal theory behind Mueller’s obstruction case against Trump. Before Mueller’s report was released, Barr released a memo describing its contents that was so misleadingly pro-Trump that Mueller sent him a private note complaining about it. And hours before the press release, Barr held a press conference in which he spun its findings in Trump’s favor, saying (for example) that the report found “no collusion,” when it expressly did not make any judgments about whether the president “colluded” with Russia in any fashion.

All of this has made it seem like Barr is acting as Trump’s personal lawyer, and not in the attorney general’s role as defender of the justice system. Now we know that more than 400 federal prosecutors, who served in administrations of both major parties, are willing to put their names on a letter saying that Barr is wrong.

It’s another blow to the credibility of an attorney general already reeling from a rough day of testimony at the Senate last week, a performance so dismal that it led several Senate Democrats to call for his impeachment.