Andrew McCabe, second-in-command at James Comey’s FBI, is at it again. First, he and his boss shredded the Bureau’s reputation as the world’s leading law enforcement agency. Now, McCabe is compounding the damage by making wild, self-serving charges to sell his new book. In one TV interview, he said it is ‘possible’ that Donald Trump is a Russian agent.

Serious charges need serious proof. Simple fairness demands it. But McCabe presents none. That’s par for the course. Simple fairness was not the hallmark of the Comey-McCabe era. No disinterested observers think the Bureau’s investigation of Hillary Clinton’s email server was treated the same way as the amorphous charges against the Trump campaign. That bias wasn’t the fault of FBI field agents. Comey pulled the investigation away from them and gave it to his inner circle. They were men on a mission. It was not a mission for blind justice.

Their double standards were clear when they passed out immunity to all Hillary’s top aides without demanding full testimony in return, when they destroyed Clinton staffers’ computers and cell phones without preserving the evidence, and when they wrote a memo clearing Mrs Clinton before she had been interviewed. Comey, whose incompetence is rivaled only by his smug self-righteousness, then held a press conference that both smeared and cleared Hillary. It smeared her with evidence that should never have been revealed unless she was charged. It cleared her by whitewashing the crimes she should have been charged with.

Comey, McCabe, and their cronies had no intention of serving up the same softball to Trump. No, siree. The Bureau relied on thin, biased evidence to obtain warrants to spy on Carter Page (really, on the Trump campaign). That evidence consisted mainly of opposition research against Trump, conducted by a former British spy and paid for by Clinton through two cut-outs. The FBI and DOJ knew the political origins, the dicey source, and the lack of verification. Instead of disclosing all that to the courts, they falsely said it was verified and hid the source’s bias. They put a cherry on this cow patty by including a Yahoo news article as additional evidence. They never told the judges it came from the same source as their other ‘evidence,’ not from independent reporting. There are words for this kind of dodge. They are found in the criminal statutes.

McCabe’s central role in this sleazy operation comes on top of a scathing report about his conduct from the Department of Justice’s Inspector General. It concludes that McCabe leaked information to the media and then lied about it to investigators on three occasions. He is now under criminal investigation for those actions. (McCabe doesn’t exactly deny the leaks but says Comey authorized them. Comey denies it.) That leaking and lying (alleged, alleged), plus McCabe’s lack of proof for his recent claims, suggest his comments are little more than hyperbole, designed to inflate his standing among Trump-haters.

Make no mistake: McCabe’s charges against Trump are extremely serious, especially since they come from a former top law-enforcement official who was involved in pertinent investigations. Any president who acted as agent of a hostile foreign power would have committed ‘a high crime and misdemeanor,’ worthy of impeachment and conviction. In fact, it would be the gravest crime against our nation since the Confederate states seceded.

So far, the public evidence does not support McCabe’s grave accusations. That’s significant because multiple investigations have been underway for a long time. The intensive probe by Special Counsel Robert Mueller has not yielded a single charge of conspiracy involving the Trump campaign and the Russians. Finding out if there was such collusion was one of the two reasons Mueller was appointed. (The other was to investigate Russian interference in the 2016 election, whether or not it involved either campaign.) A number of Russians have been charged with interfering with US elections and some US citizens have been charged with various offenses, but none involve collaboration between US citizens and the Russians during the 2016 campaign. The charges against former Trump campaign manager Paul Manafort are serious, and he has already been convicted on some of them, but, once again, none involve the Trump campaign conspiring with Russia.

There is a major caveat here. Mueller’s investigation is not finished and we don’t know if he will conclude his work with some conspiracy charges. But, as McCabe knows, the Special Counsel would already have brought such charges against Manafort and others if he could substantiate them.  He hasn’t brought any.

The Senate Intelligence Committee hasn’t found any conspiracy either, and they have been investigating on a bipartisan basis for two years.

McCabe knows all that, but he’s still flinging dung. After we wipe it off, we can ask of him, as the Army’s Chief Counsel, Joseph Welch, once asked of Joe McCarthy, ‘Have you no sense of decency, sir, at long last? Have you left no sense of decency?’

In McCabe’s case, as in McCarthy’s, the question answers itself.

Charles Lipson is the Peter B. Ritzma Professor of Political Science Emeritus at the University of Chicago, where he is founding director of PIPES, the Program on International Politics, Economics, and Security.