IMHO, I would drop this line of attack if I were Donald. It wreaks of desperation, of a candidate who knows he’s doomed. It’s like the underdog in the Superbowl blaming the refs ahead of the game to excuse the loss in advance.
A lot of such things have two different lights under which they can be put.
However this could be viewed as a signal to those who are close to on the fence. Commit yourselves.