What rhetorical devices do they use, and why do you think they are so effective?

Answer 1

do yuo mean a mneumonic device? (a way of remembering something like the colors of the rainbow..ROYGBIV?) if so they are effective simply because the brain can retain only a fraction of what is required in short term memory while storing the actual required data in long term memory....the mneumonic device "jogs" the memory into finding the required data

Answer 2

If you are talking about the media devices in persuading people, then I think presenting opinions is always the first thing. Second the news can always be twisted and accent can be placed on the thing they want to emphasise. One rhetorical device might be for example to link news to emotions. By showing personal stories that touch everyone of us, the media involves us and shapes our attitudes towards the things happening.