"Hey." So went the subject line of a campaign email blasted to tens of millions of President Obama's supporters, as if the leader of the free world was just checking in to see whether they wanted to grab a couple of drinks after work. Some other gems included the even briefer "Hi," the more suggestive "About Tonight," and — need anything more be said? — "Clooney." The emails were a widespread source of mockery, and Jon Stewart captured the frustration of many when he said, "I'd mind it less if your subject line emails were, 'Give me money.'" But it turns out there was a fastidious science behind the emails, which comprised the bulk of Obama's whopping $690 million online fundraising haul, says Joshua Green at Bloomberg Businessweek:

The appeals were the product of rigorous experimentation by a large team of analysts. "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. "When we saw something that really moved the dial, we would adopt it," says Toby Fallsgraff, the campaign's email director, who oversaw a staff of 20 writers.

It quickly became clear that a casual tone was usually most effective. "The subject lines that worked best were things you might see in your inbox from other people," Fallsgraff says. " 'Hey' was probably the best one we had over the duration." Another blockbuster in June simply read, "I will be outspent." According to testing data shared with Bloomberg Businessweek, that outperformed 17 other variants and raised more than $2.6 million.

With the campaign over, Obama's supporters may feel they can laugh about those overfamiliar emails now. But wait: "There's more to come," says Jeremy Bird of Obama for America. The president's "vaunted field operation will continue to function in support of Obama," says Jennifer Epstein at Politico, as the president seeks to enact his second term agenda. Which means supporters in the coming years can look forward to Obama dropping in to say hello every once in awhile.