Rep. Alexandria Ocasio-Cortez on Sunday used her formidable social media presence to play 2020 Democratic gatekeeper and told John Delaney, the former representative from Maryland, to "please sashay away" after he labeled Medicare for All “not good policy.”

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Delaney, who was addressing the California Democratic Convention, was overwhelmingly booed when he raised concerns about the policy that would kick "150 million Americans off their health care." He said the initiative may sound good but “it’s actually not good policy, nor good politics.”

Medicare for All is a proposal that would put the government in charge of most health benefits. The AP recently reported that polls suggest that Democrats approve the idea, but many are hesitant about an abrupt shift from private insurance. Some are calling on a more incremental approach toward single-payer health care.

Sens. Kamala Harris of California, Cory Booker of New Jersey and Kirsten Gillibrand have voiced their support for single-payer but have room for private insurance companies to still play a role in the system.

Warren told a voter at a Virginia town hall last month that it’s not “inconsistent” to pursue Medicare for All as well as smaller steps to get there, such as lowering the age for Medicare eligibility.

Some estimates put the 10-year cost of the plan at more than $32 trillion. Sen. Bernie Sanders said at a Fox News town hall that it would mean many Americans would "pay more in taxes." But he also argued the plan's costs would replace premiums and deductibles already being paid by American families, claiming many would pay less in the end.

Delaney was booed for his comments at the convention and tried to clarify that he is in favor of universal health care. But the crowd continued to boo.

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“We should have universal health care,” he said. “We should have universal health care. We should have universal health care, but it shouldn’t be a kind of health care that kicks 150 million Americans off their health care. That’s not smart policy.”

Ocasio-Cortez took to Twitter to call on Delaney to step aside.

“Since there’s so many people running for President (& not enough for Senate), instead of obsessing over who‘s a “frontrunner,” maybe we can start w some general eliminations. This awful, untrue line got boo’ed for a full minute. John Delaney, thank you but please sashay away,” she posted.

Fox News' Adam Shaw and The Associated Press contributed to this report