ATLANTA — Referring to the crowd of progressive conference-goers as President Trump's "worst nightmare," Sen. Elizabeth Warren, D-Mass., tore into members of her own party who believe Democrats should move toward the center in a fiery speech at Netroots Nation.

In the Saturday morning keynote, Warren singled out a July op-ed in the New York Times written by Mark Penn and Andrew Stein titled "Back to the Center, Democrats." The headline itself was enough to draw a loud chorus of boos from the audience.

"It was all about how we have to stop caring about 'identity politics' and how we have to stop waging 'class warfare,'" Warren said, mocking the idea that "the path forward" for Democrats involves locking up "non-violent drug offenders and ripping more holes in the economic safety net."

"We've been warned off before," Warren observed. "Give up, keep your heads down, be realisitic, act like a grown up, keep doing the same old, same old."

"But here's what's interesting," she continued. "Instead of lots and lots of ferocious back-and-forth and piling on, this time, no one cared. Big yawn. Why?"

Because, Warren asserted, Democrats are not going back to the center. The senator specifically argued the party "won't go back" to the days of welfare reform, being "lukewarm on [abortion] choice," and making empty promises on universal healthcare.

But contrary to Warren's contention, far from "no one [caring]," Penn and Stein's op-ed sparked days of debate among Democrats online. And having just targeted centrist Democrats for criticism, Warren pivoted to argue that in-fighting is harmful to the party. "We can't waste energy arguing about whose issue matters more, and who in our alliance should be voted off the island," she said.

"We are looking ahead and we will not, we shall not, we must not, allow anyone to turn back the clock," Warren said, further cautioning Democrats against a slide to the center. The senator also assured supporters that "Trumpcare" would not receive a single Democratic vote, "not now, not ever."

Reflecting on the recent history of the progressive movement, Warren said the activists at Netroots, where there are all-gender restrooms and panels on intersectionality, no longer represented only "a wing" of their party.

"We are the heart and soul of the Democratic Party," she told the sea of activists gathered in Atlanta.

Emily Jashinsky is a commentary writer for the Washington Examiner.