The downside of the tactic is that it costs a lot. “Prospecting is expensive,” Watts added. You’ve got to mail the fliers—nearly $2.5 million, or about a quarter, of what Carson spent in the third quarter was categorized as postage-related—and you’ve got to have human beings making those telemarketing calls. And even when the investment pays off, what it yields are small-dollar donations—$25, $50, $100—rather than anything approaching the $2,700 maximum.

While direct mail has its detractors, even its champions argue that the goal is to spend less on it over the course of a campaign—to make direct mail obsolete. As a campaign builds its donor file, it can return to those supporters repeatedly, convincing them to give a little more each time. Carson’s campaign burn rate actually increased in the third quarter, from 64 percent in the second quarter, but Watts said the fundraising costs are down.

“We spent 54 cents on the dollar to raise money this quarter,” he said. “Last quarter we spent 64 cents on the dollar. That is an 11 cent reduction. I expect we’re probably going to have a 10 or 11 cent or maybe more reduction the next quarter.”