The New York Times uses the presidential debates between Bush and Kerry to teach a trial advocacy lesson on the difference between direct examination and cross examination.
Christopher Scanlan writes (excerpt):
Unlike its rhetorical opposite, the closed-ended question, which limits possible answers to yes, no and “I don’t know,” open-ended questions require an expansive response. If questions are the traffic signals that direct an interview, open-ended questions are green lights, closed-ended are reds.
***
Closed-ended questions sound tough, but they also seem biased to many ears. Their narrow focus implies that the questioner believes there is only one truthful answer. . . .
***
How did this affect the debate? Open-ended questions, interviewing experts say, do a better job of uncovering emotional responses. . . .
***
This is not to say that closed-ended questions have no place in an interview or a debate. There are times when nothing but an unequivocal answer will do. . . . Having the right mix is what matters.
It seems that these candidates are masters at giving information that is non-responsive to be sure you know what they wish you to know. These techniques presume that the answerer will limit themselves to the scope of the question. In a courtroom you would get an admonishing instruction. In political debates, they sometimes never answer the question.