After doing her signature “pinky promise” with a line of little girls, but before taking the stage to deliver her stump speech to the crowd assembled in a middle-school gym in Concord, N.H., Elizabeth Warren sat in a butter-yellow classroom to explain what keeps her going.

Persistence has been the defining characteristic of the Massachusetts senator’s campaign: the battle cry that made her a progressive icon, and the quality that could propel her through a long slog to the Democratic presidential nomination. In person, Warren is still an Energizer Bunny of ideas and optimism, with no hint of alarm at her position in the polls. Her campaign has become a test case for what many well-educated liberals wish to believe: that Democrats are sane, that policy matters, and that if a smart, qualified woman just works hard enough, she can come out on top.

But what happens, I asked, if Warren tells thousands of little girls that a woman can be President, but she doesn’t win herself? What does persistence mean without results?

“Look,” Warren begins. She is quiet for a long moment, leaning forward in her plastic chair with the intensity of someone who wants to make sure she gets this right. “We have to show that we’re willing to take the risk,” she says slowly. “Because if we’re not, then women will never win.”