Former FBI Director James Comey will testify before the Senate Intelligence Committee after Memorial Day, and he’ll no doubt face lots of questions about claims that President Trump tried to tamper with the Russian-meddling probe. Let’s hope he also gets asked a few follow-ups about this:

“A number of things had gone on which I can’t talk about yet that made me worry that the [Justice] Department leadership could not credibly complete the investigation and decline prosecution without grievous damage to the American people’s confidence in the justice system,” Comey told the Senate Judiciary Committee early this month, before Trump fired him.

He was talking about the Hillary Clinton email probe, and went on to say that Bill Clinton’s tarmac meeting with then-Attorney General Loretta Lynch was the “capper” that made him certain that Justice “cannot, by itself, credibly end” the investigation.

What “things” had “gone on,” precisely? Critics of that probe have faulted Justice’s failure to issue subpoenas for key evidence, instead giving core Hillaryites immunity in exchange for handing it over, as well as the decision to allow pretty much all Clinton’s top aides to use the same lawyers — and even to allow some of them to serve as legal counsel to others.

Maybe Comey was furious at Justice higher-ups for making calls that compromised the investigation, or maybe he simply thought it made it impossible for them to credibly announce that Clinton would face no charges.

We have no desire to relitigate last year’s scandals. But, with the team Comey assembled for the Russia probe still illegally leaking details of the investigation as late as last Friday, it’s pretty important to understand exactly how the former director saw his overseers in the Obama years.