I notice that as the Pirate "wave" recedes, support for the CDU is rising. Are there really that many Pirate/CDU switchers?
I doubt the two developments have anything to do with each other. I can imagine Pirates supporting basically any other party more than the CDU.
Well, many people supported the Pirates because it was a very popular thing to do at the time (you could say a "fad"). And Angela Merkel is popular too!
Some of the more apolitical swing voters tend to support the party who gets the greatest news coverage. The Pirates certainly attracted many people from that group.