A term coined by Floyd Allport a century ago to describe what appears to be rapid shifts in public opinion. Basically "everyone wants X but thinks that nobody else does. Then some outside factor makes it possible for people to choose X, and everyone does. Everyone is surprised – “Gee, I thought all you guys wanted Y, not X .” It looks like a rapid change in opinion, but it’s not."
Changes in smoking laws, the NYC pooper-scooper law, and the sudden drop of Confederate battle flags from Wal*Mart, Sears, Target, and NASCAR (!).