My impression of advertising is that there is a lot of magic involved and no one is precisely sure what works, and a lot of it is just about keeping the brand name in people's minds or making them aware a product exists.

Certainly the once or twice I've agreed to do a market research questionnaire its involved a lot of me saying either "nope, not seen that one" or "yes!! I've seen that!! No I've no idea which supermarket it was for". I assumed there celebrity endorsements were just about catching people's eyes.

In the case of Trump and Clinton, you can hardly be unaware that there's a contest going on, which is why (until I read the article) I thought celebrity endorsements were kind of pointless.