In the matter of Robert Mueller’s investigation of the Trump-Russia connection, administration apologists make three significant claims in an effort to discredit the former F.B.I. director’s work. Let’s have a look at them:

First, they insist that the intelligence dossier compiled by British ex-spook Christopher Steele that’s one basis for the F.B.I.’s own investigation has been discredited or is at best uncorroborated. In the same vein, they claim that Fusion GPS, the research firm that helped pay Steele for the dossier, is little more than a “sleazy operator.”

The truth about Fusion is that it is paid to dig up dirt by whoever is willing to pay for the dirt. Its business model relies on the Beatles’ timeless insight that “everybody’s got something to hide except me and my monkey.”

But questions about Fusion’s credibility, client list or aggressive tactics are irrelevant. Fusion brokered the dossier but Steele produced it. What’s relevant is his credibility, the reliability of his sources and the truthfulness of their claims.

These check out. Bill Browder, the anti-Putin campaigner who is an outspoken critic of Fusion, calls Steele “a top-class person whose reputation is beyond reproach.” At least one of Steele’s possible Russian sources was found dead and three others were charged with treason, suggesting, as one Wall Street Journal news account noted, that the Kremlin was cleaning out the moles who had betrayed its hand in last year’s election meddling.