Since Bolton is a member of the Republican party, the House and even Senate Republicans can't claim that he is a Dem partisan. They won't be able to ignore what-Trump-and-his-administration-did things he might testify to under oath. Coming from him, it would probably be pretty explosive. I'm just hoping he'll do the right thing and agree to testify without forcing the court process to go all the way. He's probably annoyed he's being asked to tell what he knows in Congress rather than in the book he's drafted.