Another debate, another airing of the dirty Democratic laundry over what’s becoming the primary’s defining issue: Medicare for All.

This dicey topic, which polls poorly with the general public, features lots of Dem-on-Dem violence, not least because the proposal doubles as a tacit argument that Obamacare—the top Democratic accomplishment of a generation—is insufficient.

Until now, Medicare for All has been exhibit A of how 2020 Democrats have lurched leftward toward a radical agenda. Thursday night, though, something different happened.

This was the first debate where Elizabeth Warren and Bernie Sanders were on defense, having to fend off blows coming from Joe Biden, Amy Klobuchar and Pete Buttigieg, as a clearer divide emerged between Democrats who support another massive overhaul and Democrats who want to allow the public to keep their private health insurance plans, while also allowing for a public option.

Up until now, there had been a sense that Joe Biden had been occupying an unpopular and untenable position while all of the energy was coming from the progressives. There was also a sense that the second-tier candidates remaining (who should have been occupying moderate territory) were afraid to own that brand—either because they felt Biden already had it locked up—or (more likely) because they sensed that pandering to the progressive base was a better move than backing a more small-P progressive plan that is popular with the general electorate.

Perhaps because the field had winnowed, with just 10 Democrats left on the debate stage, several of the presumptive moderates made a conscious decision to break with Warren and Sanders who, after all, appear to have the left side of the market cornered. Candidates who had previously been tentative quit pulling their punches.

“While Bernie wrote the bill, I read the bill,” Klobuchar said, after Sanders repeated his “I wrote the damn bill” line. "And on page eight—on page eight of the bill—it says that we will no longer have private insurance as we know it." She drove the point home: “I don’t think that’s a bold idea; I think it’s a bad idea.”

Klobuchar also suggested that Sanders’ plan would kick 149 million Americans off of their private health insurance (more recent census bureau estimate suggests it’s more like 181 million).

“T he problem, Senator Sanders, with that damn bill that you wrote, and that Senator Warren backs, is that it doesn't trust the American people,” said Pete Buttigeig—who might have finally decided to match his moderate temperament with some moderate policy positions. “I trust you to choose what makes the most sense for you. Not my way or the highway,” he continued.

Kamala Harris, who once boasted of co-sponsoring Sanders’ Medicare for All plan, took an even more transparent approach, suggesting that she changed her mind on the issue “because that's what people want. And I agree, we shouldn't take choice from people.”

“ It felt like a turning point—and a healthy one, if you’re rooting for a Democrat to beat Trump in 2020. ”

Biden got in on the act, too. "I know that the senator [Warren} says she's for Bernie, I'm for Barack," he said. "My distinguished friend, the senator on my left, has not indicated how she pays for it," he continued.

Pushing back on Sanders’ suggestion that, absent Medicare for All, cancer victims would be led to “financial ruin,” Biden said: “I know a lot about cancer, let me tell you something: It's personal to me. Let me tell you something: Every single person who is diagnosed with cancer or any other disease can automatically become part of this plan. They will not go bankrupt because of that.”

Biden also took a jab at Sanders’ suggestion that union members who previously negotiated health-care benefits would be compensated by employers during the transition to Medicare for All, Biden said: “For a socialist, you've got… a lot more confidence in corporate America than I do.”

Meanwhile, Warren and Sanders seemed to be on the defensive, with Warren twice dodging a direct question about whether taxes would go up under the plan and both candidates offering evasive answers about how they would pay the vast bill for the proposal.

But the key here wasn’t Biden or Bernie or Warren, but the second-tier would-be moderates, who, on Thursday, finally started throwing elbows—at least, when it came to health care. It felt like a turning point—and a healthy one, if you’re rooting for a Democrat to beat Trump in 2020.