Three presidential hopefuls – Joe Biden (D), John Delaney (D), and Sen. Michael Bennet (D-CO) – slammed Sen. Elizabeth Warren’s (D-MA) Medicare for All plan on Friday, saying her pitch is “simply not believable.”

On Friday, Warren unveiled her highly anticipated plan for Medicare for All, providing details on how she would pay for the $52 trillion proposal, which would require roughly $20.5 trillion in new spending over the next decade. She proclaimed that her plan would not require a middle class tax hike, proposing to pay for the multitrillion-dollar program by increasing her “Ultra-Millionaire Tax,” slashing defense spending, providing a pathway to citizenship for illegal immigrants, and repurposing existing costs. The latter, for example, would require companies with more than 50 employees to make payments to the government in the form of an “Employer Medicare Contribution,” which she argues would replace the existing payments they make to healthcare providers.

However, some of her 2020 rivals are already taking issue with her lofty proposal.

Bennet released a statement asserting that her plan is “simply not believable.”

“Voters are sick and tired of politicians promising them things that they know they can’t deliver,” he said in a statement. “Warren’s new numbers are simply not believable and have been contradicted by experts.”

“Regardless of whether it’s $21 trillion or $31 trillion, this isn’t going to happen, and the American people need health care,” he added.

Biden, through his deputy campaign manager, Kate Bedingfield, also blasted the Massachusetts senator’s plan.

“For months, Elizabeth Warren has refused to say if her health care plan would raise taxes on the middle class, and now we know why: because it does,” Bedingfield said, according to the Hill.

“Senator Warren would place a new tax of nearly $9 trillion that will fall on American workers,” she continued:

There’s no two ways about it, we cannot defeat Donald Trump with double talk on health care — especially not about the impact and cost of a proposal to completely dismantle our health care system and eliminate employer-sponsored and all other private health insurance.

Biden has emphasized building on Obamacare and even promoted it in a tweet on Friday:

When it comes to health care, many Americans can't afford to wait for far off promises. Obamacare's open enrollment begins today. Head to https://t.co/2Ls3d80By6 to find an affordable, quality plan that works best for you. #GetCovered — Joe Biden (@JoeBiden) November 1, 2019

John Delaney (D), who has remained a consistent critic of Warren’s lofty proposals and “fairy tale economics,” also took aim at Warren’s proposal.

“I was the first person to point out the flaws of Medicare4all and I’m the only one with a real universal healthcare plan that works. @ewarren numbers don’t add up and the ‘public options’ Dems don’t go far enough,” Delaney wrote. “BetterCare is the only sensible universal healthcare plan.”

“A ‘public option’ is a government run insurance company that does not go nearly far enough in addressing the inequality in our healthcare system,” he continued.

“We need universal healthcare; most developed nations have universal healthcare,” he added. “But Medicare4all is a bad plan, BetterCare works”:

I was the first person to point out the flaws of Medicare4all and I'm the only one with a real universal healthcare plan that works. @ewarren numbers don't add up and the "public options" Dems don't go far enough. BetterCare is the only sensible universal healthcare plan. — John Delaney (@JohnDelaney) November 1, 2019

A "public option" is a government run insurance company that does not go nearly far enough in addressing the inequality in our healthcare system. We need universal healthcare; most developed nations have universal healthcare. But Medicare4all is a bad plan, BetterCare works. — John Delaney (@JohnDelaney) November 1, 2019

Seemingly anticipating the backlash, Warren challenged her competitors to lay out the “true, full costs” of their healthcare proposals following her plan’s release Friday morning.

“I am fighting for #MedicareForAll,” Warren said. “I have the only detailed plan to pay for it.”

“And we are the only Democratic primary campaign that has laid out the true, full costs of any health care plan, Medicare for All or otherwise,” she continued. “I look forward to others doing the same”: