Teddy couldn't give a straight answer to any question unless he had one of his handlers whispering the answer in his ear. As for coherence --- he never had any.
The guy was an intellectual zero.
A talk show host in Boston had an audio clip (unfortunately lost among station sales and mergers) of Kennedy running a committee meeting while drunk. Had to have a handler whispering corrections for just about every line he spoke:
"We're about bill Sxxx..." "No, bill Syyyy"
"...about ABC..." "No, XYZ..."
"...urge to vote against it..." "No, for it."
Etc.
But they kept voting him in.