A dangerous message is spreading in the Democratic presidential race. The message, delivered in this week’s debates by three of the top four contenders, is that Democrats and journalists who challenge left-wing ideas are parroting “Republican talking points.” The candidates who issued this rebuke—Sen. Elizabeth Warren of Massachusetts, Sen. Bernie Sanders of Vermont, and Sen. Kamala Harris of California—are trying to cow their critics. And they’re implying that if you don’t support an emerging progressive orthodoxy, you don’t belong in the Democratic Party.

This message is false and self-destructive. It narrows the party and suppresses constructive dissent. “Republican talking points” is a Democratic talking point that helps the GOP.

In Tuesday’s debate, several centrists—Gov. Steve Bullock of Montana, Rep. Tim Ryan of Ohio, former Rep. John Delaney of Maryland, and former Gov. John Hickenlooper of Colorado—went after Sanders and Warren for their “Medicare for All” proposal. Some argued that the math didn’t add up—for example, that Medicare-level reimbursements wouldn’t keep rural hospitals afloat. Others objected that the bill was coercive. “Americans [are] used to being able to make choices, to have the right to make a decision,” said Hickenlooper. In Wednesday’s debate, former Vice President Joe Biden and Sen. Michael Bennet of Colorado made similar points against Harris, although her proposal would allow more of a role for private insurers.

The centrists also offered political objections. They argued that Americans would rebel at having to pay higher taxes and at being told to give up their private insurance. They pointed out that unions had negotiated health insurance plans for their members and wouldn’t take kindly to losing those plans. A backlash against such ideas could cost Democrats the 2020 election, the centrists warned. Or it might paralyze the health care debate while uninsured people continued to die. The better course, according to the centrists, was to build on the Affordable Care Act by offering a government-run plan—a “public option”—as an alternative to private insurance.

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The leftists made good points in rebuttal. Sanders noted that patients on private insurance are already constrained by network limits on which doctors they can see. A single-payer system, he argued, would eliminate those barriers. Sanders and Harris also pointed out that the current system is inherently disruptive, since people have to change insurance when they change jobs. In addition, Sanders reasoned that if the government took care of health insurance, unions could focus their bargaining on wages instead.

These are constructive arguments. But in a political campaign, it’s tempting to go beyond such arguments and resort to more potent visceral attacks. That’s what Warren and Sanders did on Tuesday. And on Wednesday, Harris, Sen. Cory Booker of New Jersey, and former Housing and Urban Development Secretary Julián Castro followed their lead.

Warren and Sanders depicted the centrists as weaklings, cowards, and sellouts. Sanders called them “Democrats afraid of big ideas.” Warren accused them of “spinelessness” and refusing to confront problems. When Delaney disputed Sanders’ insurance math, Sanders snapped that perhaps Delaney had “made money off of health care.” Sanders also insinuated that CNN’s Jake Tapper was criticizing the Sanders bill because “the health care industry” was advertising on CNN.

The left’s main talking point was “Republican talking points.” When Delaney warned against taking away private health insurance, Warren said Democrats should “stop using Republican talking points.” When Hickenlooper objected to the Green New Deal’s broad promise of government-funded jobs, Warren accused him of using a “Republican talking point” to pretend that “we don’t really have to do anything” about climate change. When Tapper asked about raising taxes to pay for Sanders’ health care bill, Sanders retorted, “Your question is a Republican talking point.” After the debate, when CNN’s Anderson Cooper asked Warren what she would say to Americans concerned about having to “give up their private insurance,” she rebuked him: “I really wish we’d stop using Republican talking points.”

In Wednesday’s debate, Harris followed suit. When Bennet cautioned against raising taxes and eliminating employer-based insurance plans, Harris fired a shot across his bow: “We cannot keep with the Republican talking points on this. You’ve got to stop.” When former Vice President Joe Biden objected to decriminalizing illegal immigration, Booker accused him of “playing into Republican hands.” And when CNN’s Don Lemon reminded Castro that “President Obama’s homeland security secretary, Jeh Johnson, whom you served with,” had written an op-ed against border decriminalization, Castro shot back: “Open borders is a right-wing talking point. And, frankly, I’m disappointed that some folks, including some folks on this stage, have taken the bait.”

The “talking points” attack is unhealthy for several reasons. To begin with, it’s false. The concerns raised by Biden, Bennet, and others aren’t coming from Republicans. They’re coming from policymakers who have spent their careers in the Democratic Party.

Second, the centrists are offering good ideas, and their criticisms are connected to those ideas. Delaney has a market-based plan to tax carbon, develop a “private innovation economy” for carbon capture, and disperse the profits to build political support for addressing climate change. Pete Buttigieg, the mayor of South Bend, Indiana, is proposing “Medicare for all who want it”—a public option that could grow into a single-payer system, but only if consumers choose it.

By framing centrist ideas as Republican, the left is helping the GOP .

Third, the centrists’ criticisms can sharpen the left’s ideas. Sanders’ college subsidy plan will be less expensive, more likely to pass, and less likely to hurt Democrats in elections if he excludes rich families from it, as Sen. Amy Klobuchar of Minnesota has proposed. Castro is more likely to get what he wants on immigration—blocking the separation of parents from children at the border—if Democrats target that policy directly instead of trying to decriminalize unauthorized entry. And Harris’ version of Medicare for All, which lets private insurers compete with the government if they meet the same rules for coverage and fees, is itself a response to criticisms of the Sanders bill. The left’s idea of Medicare for All is evolving and converging with the centrist idea of an expanding public option.

Fourth, by framing centrist ideas as Republican, the left is helping the GOP. If you tell voters that anyone who worries about tax increases, opposes free college for rich kids, supports the availability of employer-based health insurance, or thinks border jumping should remain a crime is really a Republican, the whole electoral map will turn red.

Take the question of health care. A month ago, at a Democratic debate, all 10 candidates on the stage raised their hands when they were asked whether “your government plan would provide coverage for undocumented immigrants.” In Tuesday’s debate, Ryan objected to that idea, saying it was unfair to American citizens “struggling to pay for their health care.” Some progressives didn’t like his answer. But in a CNN interview after the debate, Warren predicted that the general election would pit Trump’s message of blaming immigrants against her message of blaming the rich. If that’s how the election unfolds—and if Warren has to defend a platform of taxpayer-funded health care for undocumented immigrants—won’t that help Trump make his case? Shouldn’t Democrats debate this “Republican talking point” before they face it for real?

In Wednesday’s debate, Biden argued for an increase in legal immigration. “The reason we’re the country we are is we’ve been able to cherry-pick from the best of every culture,” he said. For example, he proposed, “anybody … with a Ph.D., you should get a green card for seven years. We should keep them here.” Instead of embracing this proposal, Booker attacked it. “This really irks me, because I heard the vice president say that if you got a Ph.D., you can come right into this country,” said Booker. “That’s playing into what the Republicans want, to pit some immigrants against other immigrants.”

No, it’s not. Favoring immigrants based on merit criteria, such as job skills and advanced degrees, has been a Democratic idea since the 1960s.

Democrats have a lot of advantages in the coming election. They’re running against a deeply unpopular president, and voters largely share the progressive outlook on universal health care, college affordability, taxing the rich, and raising the minimum wage. The dumbest thing Democrats could do is alienate those voters by disowning the mainstream. “Republican talking points” is a talking point that only helps Republicans.