The most progressive candidates on stage at the Democratic presidential primary debate in Detroit on Tuesday, Sens. Elizabeth Warren, D-Mass., and Bernie Sanders, I-Vt., dominated the event — despite a bizarre decision by the host network, CNN, to frame the discussion as a running critique of their far-reaching policy proposals to reform the federal government.

As Yousef Munayyer, a Palestinian-American policy analyst observed, “CNN set up this debate as a multi-front ambush on Warren and Sanders.” Indeed, the entire structure of the debate, starting with the first questions about Medicare for All, introduced by Sanders and supported by Warren, was based on the premise, recently popular with pundits, that Democrats are in danger of moving too far to the left.

That framing led to the bizarre opening exchange in which a fringe candidate, former Rep. John Delaney, D-Md., was invited by moderator Jake Tapper to attack the two highest-polling candidates, Sanders and Warren, for planning to replace the private health insurance industry with a government-run plan. In a forceful rebuttal to Delaney, Warren pointed out that by accusing Sanders of wanting to take people’s private health insurance away, the former Democratic congressman was channeling the Republicans.

“Let’s be clear about this: We are the Democrats,” Warren said in a moment that was tweeted out by her campaign. “We are not about trying to take away health care from anyone. That’s what the Republicans are trying to do, and we should stop using Republican talking points in order to talk with each other about how to best provide that health care.”

Sanders and Warren were then pressed repeatedly by Tapper to say if moving to Medicare for All would require some middle-class families to pay more in taxes. Sanders noted that middle-class families would pay less overall — because any increase in taxes would be less than their current costs for insurance and deductibles. And he slammed Tapper for the premise of the question — which is, as he pointed out twice, a Republican talking point. “And by the way,” he added, “the health care industry will be advertising tonight on this program … with that talking point.”

“Why doesn’t CNN ask basic questions about drug companies gouging the public, or the health care industry using its largesse to manipulate the media and Congress to maintain the status quo,” my colleague Lee Fang tweeted. “Why only this narrow question about taxes that never gets asked about other policy demands?”

When Tapper then put forward the argument against Medicare for All offered by Joe Biden — that union members who have fought for good health care plans should be allowed to keep them — Sanders shut down criticism by Rep. Tim Ryan, D-Ohio, another centrist, of what his plan would provide. “But you don’t know that, Bernie,” Ryan interjected. Sanders replied: “I do know it, I wrote the damn bill.”

Before the debate was even over, the Sanders campaign had made those words into a sticker and was using it to solicit donations from supporters.

Delaney then criticized Sanders and Warren for not understanding the health care industry he has been part of and profited from. “I’m the only one on the stage who actually has experience in the health care business, and with all due respect, I don’t think my colleagues understand the business,” Delaney said.

“It’s not a business!” Sanders replied. “Maybe you did that and made money off health care,” Sanders added moments later, “but our job is to run a nonprofit health care system.”

As the debate wore on, the framing, which invited the low-polling centrist Democrats to attack the front-runners at center stage, irritated more and more observers.

Again and again, the moderators urged centrist candidates to voice their concerns with the proposals of Warren and Sanders. One of those questions led Warren to respond to Delaney with the signature reply of the night.

“I don’t understand why anybody goes to all the trouble of running for president of the United States just to talk about what we really can’t do and shouldn’t fight for,” Warren said to cheers.

Later, Warren even rubbed her hands with glee when Delaney was informed that his net worth of $65 million would make him subject to her proposed wealth tax.

Having constructed the entire debate to generate disagreements between the progressive candidates, whose ideas are finding support from Democratic primary voters, and centrist candidates who are struggling to get past 1 percent in the polls, CNN concluded the evening with the headline it had worked so hard to create: “Breaking News: Liberal and Moderate Democrats Clash in Detroit.”

Update: Wednesday, July 31, 3:21 p.m. EDT

The morning after the debate, the Republican party helpfully proved that Warren and Sanders were right to say that it was a Republican talking point to focus only on the need to increase taxes to pay for Medicare for All, while ignoring the fact that total costs would go down for working families that no longer have to pay outrageous premiums and deductibles.

On Wednesday morning, the Republican National Committee tweeted out video of a post-debate interview in which Chris Matthews of MSNBC repeatedly pressed Warren to say if taxes would go up, and completely ignored her point that “out of pocket costs for middle class families,” are, under the plan she and Sanders endorse, “actually going to go down.”

Warren’s supporters shared the same clip, but to praise what they called her articulate refusal to accept the premise of the question — which would, no doubt, have been instantly used in Republican attack ads.

The exchange is worth watching in full. After failing to get Warren to accept the premise of the question — in which only tax rates are discussed, and the greater savings from not paying for terrible health insurance are ignored — Matthews even insisted that “it’s not a Republican talking point.”

The more important point, Warren said is “a question about where people are going to come out economically.” As Matthews objected, “that’s not my question — my question is how much will taxes go up,” Warren replied: “Look… I spent most of my life studying families that went broke, and a huge chunk of them went broke because of high medical bills and many of them had health insurance. So the question is not, Do you have health insurance or not have health insurance? The question is how much are you going to have to dig in your pocket to pay?”

“I know that’s the answer that you’d like to give, but will your taxes go up?” Matthews asked.

“No, it is the answer,” Warren said, “the question is your total costs.”

“Okay but there’s no answer to the question, Will your taxes go up?”

“There is an answer to the question about your costs,” Warren said, “because it’s costs that matter to people.”

It seems worth noting that the copy of the video shared by the RNC on social networks also included an unexplained glitch, in which the word “broke” was deleted from Warren’s statement that her career before politics — studying bankruptcy in middle class families — meant that she had “spent most of my life studying families that went broke.”