“So I'm really shocked at the notion that anyone thinks I'm punitive,” Warren said. “Look, I don't have a beef with billionaires. My problem is you made a fortune in America, you had a great idea, you got out there and worked for it, good for you. But you built that fortune in America. I guarantee you built it in part using workers all of us helped pay to educate. You built it in part getting your goods to markets on roads and bridges all of us helped pay for. You built it at least in part protected by police and firefighters all of us help pay the salaries for.”

On her general philosophy of change, she cited her experience after the 2008 financial crash successfully promoting enactment of a new agency to protect consumers. She ignored advice from people who told her, Warren said, that she was more likely to win if she would “go for something small, go for something the big companies will be able to accept.”

Sanders struck many of the same themes: “The way you win an election in this time in history is not the same old same old. You have to inspire people. You have to excite people. You've got to bring working people and young people and poor people into the political process.”

But others disputed the idea that the way to bring change is by pushing for the most dramatic version of change, as quickly as possible, or by dismissing those who disagree as weaklings or appeasers.

On the familiar question of whether Democrats should try to expand Barack Obama’s Affordable Care Act or scrap it in favor of mandatory “Medicare for All,” Klobuchar defended the more incremental approach. “I’m tired of hearing whenever I say these things, ‘It’s Republican talking points,’ she said. "I appreciate Elizabeth’s work [but] the difference between a plan and a pipe dream is something that you can actually get done.”

On the question of imposing a “wealth tax” on big fortunes, Buttigieg professed he is “all for” it and other ideas he heard from debate rivals. “Let me tell you, though, how this looks from the industrial Midwest where I live,” he said. “Washington politicians, congressmen and senators, saying all the right things, offering the most elegant policy prescriptions, and nothing changes.”