For this to be true, the leaker would almost have to be Manafort or one of the kids? Who else is close enough to know?
Far from convinced this rumor originated with the Trump camp...
Rumor via Erickson is that Manafort leaked it. He thinks people still loyal to Corey Lendowski inform others of Manafort’s VP manipulations. It’s not out of the question.
Election team members can be incredibly petty , insecure and vindictive,
as Corey himself was reputed to have been.