Will Medicare-for-all hurt the middle class? Elizabeth Warren and Bernie Sanders struggle with questions about its impact.

The two presidential candidates who have most strenuously backed Medicare-for-all are scrambling to ease concerns that it would create higher costs for many middle-class Americans.

Sens. Elizabeth Warren (D-Mass.) and Bernie Sanders (I-Vt.) are running on a multitrillion-dollar plan Sanders wrote to provide health insurance coverage to all Americans through the federal government, rather than from private insurers. Although they have frequently stressed that the middle class would see overall costs go down, a wide range of experts — including one whom Sanders has relied upon — say it is impossible to make those guarantees based on the plans that the candidates have outlined so far.

“Obviously, all of the 180 million people who have private insurance are not going to pay less. It’s impossible to have an ‘everybody wins’ scenario here,” said Kenneth Thorpe, chairman of the health policy department at Emory University. “The plan is by design incredibly disruptive. As a result, you create enormous winners and losers.”

“There’s no question it hits the middle class,” he added.