In the rapidly shifting digital terrain of presidential campaigns, sometimes wacky works.

No one knows this better than the Obama campaign's E-mail team, which pestered supporters with dozens of off-beat fundraising E-mails—many with enormous successs. The campaign told Bloomberg-Businessweek last week that most of the $690 million raised online came from those fundraising E-mails. Notes with the subject line "Hey" were the biggest driver of those donations.