For casual followers of presidential-primary politics, there’s an easy trick to determine which candidate is leading the pack at any given moment: Who’s the first one to come under attack at a debate?

If there was any doubt that Elizabeth Warren is the new front-runner for the Democratic presidential nomination, Pete Buttigieg, Amy Klobuchar, and Beto O’Rourke cleared that up pretty quickly tonight.

Lagging contenders piled on the senator from Massachusetts at the fourth Democratic debate, in Ohio, over her refusal to explicitly say how she’d pay for Medicare for All and whether she’d raise taxes on the middle class under her plan. The issue is a familiar one at the debates, to the point of being tiresome. Warren has been asked about it by moderators at the beginning of each contest, and she answered it the same way tonight by saying that total costs would go down for middle-class families, who would no longer have to pay insurance premiums or deductibles under single-payer health care.

“I will not sign a bill into law that does not lower costs for middle-class families,” Warren said. It’s a deft but obvious dodge, because the implication is that, yes, taxes would go up for the middle class even if they pay less overall.

This time, however, the difference was that Warren’s rivals called her out for it.

“We heard it tonight: a yes or no question that didn’t get a yes or no answer,” Buttigieg, the mayor of South Bend, Indiana, said. “This is why people here in the Midwest are so frustrated with us, with Washington in general and Capitol Hill in particular.

“Your signature, Senator, is to have a plan for everything, except this,” Buttigieg continued. “No plan has been laid out to explain how a multi-trillion-dollar hole in this Medicare for All plan that Senator Warren is putting forward is supposed to get filled in.”

Moments later, Klobuchar joined the criticism, pointing out that Senator Bernie Sanders of Vermont had acknowledged that taxes would go up for the middle class—albeit far less than for the wealthy—even as their total costs would decrease. “At least Bernie’s being honest,” the senator from Minnesota said. “I think we owe it to the American people to tell them where we will send the invoice.”

Not to be outdone, O’Rourke cited Warren’s plan to levy a wealth tax on assets over $50 million in saying his rival was “more about being punitive” and pitting people against one another “instead of lifting people up.” Warren replied that she was “shocked” to be called punitive. “I don’t have a beef with billionaires,” she said, before launching into a part of her stump speech where she points out that even the most successful entrepreneurs in the country built their businesses using the infrastructure, educational system, and law-enforcement protection “that everyone paid for.”

Warren had largely escaped attacks from her rivals in the first three debates, even as she was rising in the polls. Former Vice President Joe Biden and Sanders were more frequently the target of criticism from the long-shot candidates. But in the month since the Democrats last gathered on the debate stage, Warren has overtaken not only Sanders but Biden in key national polls and in surveys out of Iowa and New Hampshire.

The tenor of the critiques Warren received tonight were far milder versions of the attacks she’ll have to fend off from Republicans if she’s the nominee—that her unabashedly progressive agenda will turn off middle-of-the-road voters, that the candidate who boasts about all her plans is being evasive about her most far-reaching proposal.

How she responds over the next few months might well determine whether she keeps her perch atop the primary race. But for Warren, being the target of everyone’s rhetorical fire is undoubtedly a good problem to have.

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