(CNN) Sen. Elizabeth Warren's silence on how she plans to pay for Medicare for All has turned into a problem at an important moment in her campaign. Right as she has become one of the clear frontrunners in the Democratic race — if not the frontrunner — she walked out of the fourth Democratic debate a bit bruised from her unwillingness to answer the question about whether she would raise taxes to pay for the benefits.

Warren has promised to release her plan about paying for the benefits. "Right now the cost estimates for Medicare for All vary by trillions and trillions of dollars and the different revenue stream for how to fund it, there are a lot of it," she said in Iowa . "This is something I've been working on for months and months, and it's got just a little more work until it's finished."

The plan will likely involve a package that mixes higher taxes and other revenue streams in exchange for eliminating the deductibles and premiums as well as other out-of-pocket expenses. Warren might make some adjustments to proposed benefits to lower the high estimates that are currently being projected.

But to take control of this debate, Warren needs to offer more than a policy brief about finance. She has the chance to turn this challenge into an opportunity to make this part of her signature issue — restoring security to middle class Americans. It's an issue that has gotten drowned out with all the emphasis on health care.

During the televised debates, the conversation about paying for Medicare for All has overwhelmed almost every other domestic issue. The good news for her and other proponents of this idea is that although polls show that 55% of Democrats would prefer to build on the existing Affordable Care Act, 51% of all Americans support a Medicare for All approach — a good sign of the potential to win votes across the aisle.

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