Is Biden's memory fair game for rival Dem candidates?

Since the left continuously questions the incumbent president’s mental state, sure. In fact, I’m wondering about the mental stability of all the fruits and nuts running, along with the fools that believe their BS.

It would be if the criticism were valid. In the case of Castro, apparently his is faulty or he is hearing impaired

I think pretty much everything that is true is fair game. Problem is, many of the accusations that politicians level are not true.
Biden has plenty in his record to shift through and make a call on.