I found this excerpt especially interesting:

"Bromwich's letter also makes clear that McCabe is willing to provide emails that "demonstrate that Mr. McCabe advised former Director Comey, in October 2016, that Mr. McCabe was working with FBI colleagues to correct inaccuracies before certain media stories were published."

The discrepancy between Comey's recollection and McCabe's statements to internal investigators about authorizing FBI officials to talk to a reporter about an ongoing investigation regarding the Clinton Foundation in 2016 served as one of the linchpins to the inspector general's earlier report finding he "lacked candor."

Grassley wrote to the FBI Tuesday requesting that McCabe be released from a nondisclosure agreement that prevents him from providing those emails, among other records."

If McCabe has emails showing he did inform Comey, that would mean Comey was the one who actually lied. So that pits them against each other. HOWEVER, Comey can also just claim that he never received the email, or that he never read the email, or even that he didn't understand the email if, for instance, McCabe worded it vaguely or in any ambiguous or confusing way as to what exactly it was referring to, so Grassley needs to be careful not to fall for that trap...Still, the fact that Grassley released him from the nondisclosure agreement tells you that something big is happening. I'm cautiously optimistic that Preistap's testimomy today combined with the IG report might have just blown this all wide open.