LAS VEGAS -- Hillary Clinton stepped up a criticism of her Democratic presidential opponent, Bernie Sanders, on Sunday night, telling supporters at a rally in the Las Vegas suburbs that the senator from Vermont would replace their insurance plans with something more expensive.

"We both share the goal of universal health-care coverage, but he wants to start all over again," Clinton said. "And he wants to have a new system that would be quite challenging because you would have to give up the insurance you have now, and it would cost a lot of money. The goal is a good goal -- I absolutely agree with that -- but the last thing our country needs now is to be thrown into another contentious debate about health care."

Clinton has frequently accused Sanders of wanting to start an impossible new health-care debate, and at the determinant of some people. At different points her campaign has said that the Sanders single-payer "Medicare for All" plan would scrap the Affordable Care Act, and that it would leave coverage decisions to capricious Republican governors.

"Based on every analysis that I can find by people who are sympathetic to the goal, the numbers don’t add up, and many people will actually be worse off than they are right now," she said at a debate last week in Milwaukee.

But the warning to middle-class voters, that the plans they enjoyed could be lost, was more pointed and harder to debunk. Sanders favors a European-style model where health insurance would "no longer be tied to employment" and "working Americans wouldn’t have to choose between bargaining for higher wages or better health insurance."