As you said, if it’s only about mishandling classified documents, this will prove to be a huge overreach. Hell, he could have declassified them before leaving office. There had better be certain specific documents they knew to be there.
I recall the outrage felt by nearly everyone with the revelations that Nixon had weaponized Federal agencies to attack his enemies. If this particular expedition doesn’t land the big fish it’s after, it will become commonplace.
but there is harm-joy (probably not a good thing, but humans are messed up in dozens of ways)
in Trump signing a law in Jan 2018 that increased penalties for mishandling classified materials.
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But hey that is just my brain trying to find music and taking delight in the artifice of it all.