Elizabeth Warren was ready for the question. She gets a variation of it almost everywhere she goes. Often, it’ll come after she’s outlined any number of the big, sweeping things she intends to do once she’s assumed the presidency—wipe out student debt, say, or bring the private equity industry to heel, or revamp the State Department. Her immodest plans tend to inspire at least a few people in every crowd to wonder the exact same thing: Really? And how do you expect you’ll do all that?

On a chilly summer evening in a high school gym in Milwaukee, I noticed she’d begun preempting the question by highlighting her own audacity.

She recounted a little story of a colleague who had once approached her on the Senate floor to suggest that an idea of hers was maybe a bit improbable. “That’s just too hard,” Warren said he told her, and added she should “smile more.” (The good, liberal crowd booed on cue.) “And here’s what I remember thinking,” she said, her voice resonating with the righteous disbelief she must have felt then. “What do you think they said to the abolitionists? ‘You’re not going to change this country, that’s too hard!’…What do you think they told the suffragettes? ‘Quit now. It’s just too hard.’ What did they say to the early union organizers? ‘Quit now. It’s just too hard.’ But here’s the thing. They didn’t quit. They persisted and they changed the course of American history!”

The stakes of Warren’s run are historically significant. She is vying to become not simply the country's first female president, but the architect of an ambitious rethinking of American government. (Her campaign’s central question is: Who does our government work for?) Yet for all the grandness of her vision, some of her shrewdest innovations on the trail can seem almost imperceptible. Consider her selfie strategy. “We’re going to take pictures,” Warren announced from the stage, shortly after invoking those trailblazers of yore. Here was a stealth weapon available to neither abolitionists nor suffragettes. “Someone will explain whether to go to that side or that side.”

For many of the hundreds of people who had turned out to hear Warren speak, this was the main event: a photo with the candidate. Quickly, a buzzing but orderly line began to snake across the gym, into the school’s hallway, and out the double doors into the street.

The selfie line has, by now, become a notorious feature of a Warren event—one that reflects the campaign’s savvy as well as the candidate's unique commitment and stamina: She stays as long as it takes to pose with every person who wants a picture. Sometimes the line is so long that this obligation requires hours of Warren’s time—as it did in Chicago in June, when over three thousand people took two and a half hours to shuffle through. “I don’t know how she does it after doing the speech and taking those questions, which is very hard,” said former Democratic Senate majority leader Harry Reid. “I’ve never known anyone to do that before. I know that when I finished my town halls, I just wanted to go home.”

Warren, however, told me that she finds the selfie line “energizing.” Earlier that day, as we chatted in her hotel, I asked her about these post-rally meet-and-greets. “The selfie line is the chance to have the direct touch,” she told me. “I get to hear from one person after another what they want me to hear. Anything! This is their chance, and they can tell me anything they want as they come through that selfie line. And it keeps me connected to people in a powerfully important way.”