More from Kevin and Orac.
Update: Many bloggers and commenters have emphasized McCain's ptosis in addition to the peripheral 7th nerve manifestations. As Steve Novella has pointed out:
Isolated ptosis would be an extremely uncommon presentation of a stroke or tumor, other signs would almost certainly be present. Ptosis is most often physiological - meaning normal for that person. This type of ptosis can also come and go, so it may be more noticable at some times than at others.
Novella points out that benign ptosis is very common and may be physiologic. If the chance of a stroke causing upper facial weakness is slim, the chance of one causing this and ptosis at the same time are slim to none.