At the AFL-CIO's National Summit on Raising Wages, Sen. Elizabeth Warren (D-Mass.) described how her childhood shaped her view of the minimum wage. (Video: YouTube: AFL-CIO)

How do you balance progressive populism with aspiration? This is one of the key questions facing Democrats (and Republicans, to an extent) going into 2016. Centrist Democrats in particular worry that too much anti-Wall Street/soak-the-rich rhetoric doesn't leave much room for upbeat and aspirational messaging -- the very kind that makes voters feel good and hopeful, rather than just pessimistic.

Sen. Elizabeth Warren (D-Mass.) has of course cornered the market on progressive populism these days, with a speaking style that makes Bill Clinton nervous.

Indeed, the last Democrat with such a passionately populist message was the pre-scandal John Edwards, with his talk of "two Americas" and being the son of a mill worker. He looked like and certainly had the bank account of an insider, but with that Southern accent and working-class background, he sounded like an outsider. (His multi-million dollar home and that haircut muddled his message a bit.)

In a speech before her "labor friends" at the AFL-CIO's "Raising Wages" summit on Wednesday, Warren showed why progressives love her. She brought a litany of stats about how the rich are getting richer and how "the game is rigged.", which has mounted a draft-Warren-for-president campaign, quickly sent out a note about the speech:

Senator Warren’s message — that it’s time to give corporate lobbyists and their trickle-down policies the boot and build an economy that works for everyone, not just the wealthy few — will define America’s economic debate for the next two years. Majorities of Americans from both parties and all walks of life agree with her that it’s time to raise the minimum wage, protect and expand Social Security and Medicare, and ensure that wealthy corporations pay their fair share. As Warren says, no one working full-time should live in poverty.

That's the kind of language -- "trickle-down policies," "corporate lobbyists" -- that has come to define Warren's speeches, her image and her take on income inequality. But what really stirred the crowd was her final peroration, about her personal journey. Unfortunately, the audio was badly garbled (snippets in a video below), but it starts with Warren's personal story, back when she was 12 years old.

I remember the day my mother, scared to death and crying the whole time, pulled her best dress out of the closet, put on her high heels and walked to the Sears to get a minimum-wage job. Unlike today, a minimum-wage job back then paid enough to support a family of three. That minimum-wage job saved our home — and saved our family. My daddy ended up as a maintenance man, and my mom kept working at Sears. I made it through a commuter college that cost $50 a semester and I ended up in the United States Senate.
Sure, I worked hard, but I grew up in an America that invested in kids like me, an America that built opportunities for kids to compete in a changing world, an America where a janitor’s kid could become a United States senator. I believe in that America.

That line about the Senate brought the crowd to its feet for a sustained ovation. It captures the kind of aspirational narrative that is the stuff of presidential campaigns and the great political speeches that can help to advance them.

Hillary Clinton can't match this rhetoric, and neither can Jeb Bush. And it's a big reason why plenty of people are hoping to hear "janitor's kid" on the same campaign trail where "son of a mill worker" was such a mainstay.