“I’ve already e-mailed you twice this month,” said a note from Sen. Patty Murray (Wash.) on behalf of the Democratic Senatorial Campaign Committee. “I wouldn’t e-mail a third time if it weren’t absolutely necessary.”

House Minority Leader Nancy Pelosi (Calif.) tried shaming supporters in a recent pitch: “Hillary Clinton asked for your help this week. President Obama asked for your help this week. So far, more than 80,000 of our best supporters have responded to their calls-to-action. But sadly, it doesn’t look like you’re on that list.”…

Democrats also say they aren’t worried about the risk of backlash — because the messages appear to be working. The DCCC has outraised the National Republican Congressional Committee by about $33 million this cycle, thanks in part to $50 million in small-dollar donations from the party faithful — most of them collected online. On average, the DCCC’s online donors give $18 in response to an e-mail, Ward said, and they usually give more than once.

Robert Epstein, former editor in chief of Psychology Today and senior research psychologist at the American Institute for Behavioral Research and Technology, said research shows that “people are far more likely to take action to avoid negative events than to produce positive ones.”