During a campaign stop in Iowa on July 4, the six-term senator declared, "This guy is brain-dead."
It's an extreme charge, since brain death is defined as "irreversible unconciousness with complete loss of brain function" (Encyclopedia of Death and Dying).
Needless to say, we find the charge ridiculous. There's no evidence Biden performed the necessary medical tests to make such a diagnosis. We would have accepted the results of a cerebral blood flow study or proof that Biden had examined Bush to see if he had an oculocephalic reflex.
Indeed, even people who disagree with the president about Iraq and assorted other issues will acknowledge that the president has spontaneous respiration and is responding to stimuli.