An interesting article on how the Obama team pulled off a very successful "get out the vote" campaign. Their winner? A simple phrase: "A record turnout is expected".
Wow. That's the same Robert Cialdini and his descriptive social norm I heard about over two years ago.
The basic idea is that "everybody is doing it" is much more powerful than "you ought to do it". We use it every time we ask somebody else if they're going to X's party, if they're contributing to their 401k, if they're tithing, if they're on Facebook, etc.
Robert Cialdini's book is: Influence: The Psychology of Persuasion (Collins Business Essentials).
Everyone is buying it.