Wolf Blitzer's failure on the popular game show, Jeopardy, is not an indication of his mental health. Jeopardy is a game of trivial knowledge, rather than a comprehensive test of someone's mental acuity. While it is unfortunate, and likely embarrassing that Wolf performed so poorly, one should not misconstrue the meaning of his performance.
Evidence of dementia is far more clear. Sundowners, a symptom where things start becoming more and more difficult to process in the evening time, is a clear symptom. Forgetting one's keys that are in one's hands, forgetting names and faces, and losing track of time are all symptoms of dementia. Failing at a celebrity game show is not a sign of dementia.
To save at Wolf Blitzer's failure on Jeopardy is some kind of evidence of dementia is a horrible thing to say. My guess is many people who would appear in a stress filled situation like a game show look like wise crack under pressure. Simply because he is a high profile person does not make him anymore or less apt to error.
No, I don't think Wolf Blitzer's failure on Jeopardy! is necessarily evidence of dementia. Other contestants have failures on the show and no one jumps to a conclusion that they have dementia. Other factors come into play in a situation like this. It is possible Wolf was not well versed in the particular categories on his episode. Perhaps he wasn't quick enough with the buzzer. Maybe he was just having a bad day.