Anyone living in the large universe of the Obama campaign’s email lists during the last year or so undoubtedly noticed the extraordinary volume, and sometimes the unusually casual tone, of requests for money or some volunteer activity. As Joshua Green reports at Businessweek, there was nothing casual about the design of these messages:

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 e-mail 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 in-box 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.

It seems the tests didn’t always accord with what Obama’s wizards expected:

Another unexpected hit: profanity. Dropping in mild curse words such as “Hell yeah, I like Obamacare” got big clicks. But these triumphs were fleeting. There was no such thing as the perfect e-mail; every breakthrough had a shelf life. “Eventually the novelty wore off, and we had to go back and retest,” says Showalter.

Fortunately for Obama and all political campaigns that will follow, the tests did yield one major counterintuitive insight: Most people have a nearly limitless capacity for e-mail and won’t unsubscribe no matter how many they’re sent. “At the end, we had 18 or 20 writers going at this stuff for as many hours a day as they could stay awake,” says Fallsgraff. “The data didn’t show any negative consequences to sending more.”

That’s bad news, since we’ll eventually have to experience the limits of our “nearly limitless capacity for email.”

Green’s account focuses on fundraising missives. But some of the other variety were interesting as well. Mid-afternoon on Election Day, I got one asking me (and I don’t know why I was getting one, since I’ve never donated to the Obama campaign nor answered any requests for help) to go to a particular location in downtown Monterery to make phone calls to battleground states (presumably to Nevada in the Pacific Time Zone).

In any event, since Obama won, we’ll see a lot more of this in the next cycle from both parties and all sorts of candidates. Let’s just hope the testing continues and we don’t all become prisoners of this year’s email fashions.

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Ed Kilgore is a political columnist for New York and managing editor at the Democratic Strategist website. He was a contributing writer at the Washington Monthly from January 2012 until November 2015, and was the principal contributor to the Political Animal blog.