It's a fear, but every presidential candidate has some loony somewhere in this country eying to gun them down over arbitrary or imaginary reasons. One of the things about Obama that brings this all to mind is his campaign message (young optimist seeking to bring out the best in the newest generation). It's a lot like JFK, though I think the RFK situation is far more comparable to that of Obama's.
Needless to say, let's pray that such a tragedy does not befall any of these candidates, regardless of whether or not we agree with them.
Good thing he didnt hold a rally at the Ambassador Hotel last tuesday then....:X