Read: The question Elizabeth Warren doesn’t want to answer

To pay for Medicare for All, Warren would impose an additional 6 percent tax on assets above $1 billion, plus she’d add a tax on financial transactions and raise capital-gains taxes for investors. About half of the money needed would come from a tax on employers: Under Warren’s plan, businesses would pay the government roughly the same amount they now pay for private insurance for their employees. To assuage concerns from unions, she’d offer a reduction to companies that agree to pass along savings to workers through collectively bargained agreements. Warren would achieve additional savings through cuts to military spending and revenue generated by comprehensive immigration reform.

In releasing such a detailed plan, Warren solves a couple of problems for herself. Her Democratic rivals can no longer criticize her for dodging the tax question, and as she looks ahead to a possible general election, she is denying Republicans an easy attack line by vowing not to soak the middle class.

But the fiscal assumptions in Warren’s plan may prove to be a target for Democrats and Republicans alike. The $20.5 trillion estimated cost is an eye-popping number, but it’s far less than the $32 trillion that think tanks pegged to Senator Bernie Sanders’s Medicare for All plan, which Warren had previously backed. That’s $11.5 trillion in fewer taxes she’d have to raise or spending she’d have to cut, and it immediately drew scrutiny from her fellow Democratic candidates.

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

Former Vice President Joe Biden’s campaign argued that Warren’s plan to tax employers would amount to a tax on their middle-class employees. “The mathematical gymnastics in this plan are all geared towards hiding a simple truth from voters: It's impossible to pay for Medicare for All without middle class tax increases,” deputy campaign manager Kate Bedingfield said in a statement. “To accomplish this sleight of hand, her proposal dramatically understates its cost, overstates its savings, inflates the revenue, and pretends that an employer payroll tax increase is something else.”

And while Warren may be shielding middle-class voters from an income tax hike, she is sticking with a plan that, if enacted, would force them to give up their private insurance in the years to come—a clear contrast with other Democrats who have said that a government plan would be optional. In outlining her plan, Warren countered that instead of protecting the choice of insurance, she’d protect the choice of doctors that too many private plans currently restrict. “Every candidate who opposes my long-term goal of Medicare for All,” she wrote, “should explain why the ‘choice’ of private insurance plans is more important than being able to choose the doctor that’s best for you without worrying about whether they are in-network or not.” Warren said that in the next several weeks, she’d release a follow-up proposal that details how she plans to transition the nation to a fully public insurance system over a period of years.