...and it isn't what's in this piece. It's in what it implies.
The three are:
1) Andrew McCabe, Deputy Director of the FBI (who targets endlessly)
2) James Baker (the Gen. Counsel of the FBI who was just reassigned)
None of this is shocking. Trump has gone after McCabe and Baker. We know that...
The writer of this piece wrote a bombshell piece in December about Trump knowing Flynn had committed a crime.
That piece was damaging to Trump but helpful to WH Counsel Don McGahn.
...and Reince Priebus was leaking all of the McGahn-related dirt.
Unlike the other doozies this author has written, this is the only one that specifically refers to "Trump Aides"... of which Reince Priebus was one.
Don McGahn isn't likely the source for this one...
I'm sticking to my original answer:
Priebus is all up in Trump's grill and throwing haymakers
...and I'm sure there are more to come