The Science Behind Those Obama Campaign E-Mails – Businessweek

“We did extensive A-B testing not just on the subject lines and the amount of money we would ask people for,” says Amelia Showalter, director of digital analytics, “but on the messages themselves and even the formatting.” The campaign would test multiple drafts and subject lines—often as many as 18 variations—before picking a winner to blast out to tens of millions of subscribers.