If the singular issue of Medicare for All becomes increasingly linked with electability — the factor that remains many Democrats’ top priority in the primary — it could spell trouble for Warren, who has already struggled with questions about whether she can beat President Donald Trump. Bernie Sanders, too, has hinged his candidacy on Medicare for All, but has faced less scrutiny — in part because he has run a campaign less focused on broad appeal to moderate voters than Warren has.

Warren has tried to deal with rising anxieties from voters over Medicare for All, and her own support of it. She traveled around Iowa last weekend days after announcing a plan to pay for a $20.5 trillion single-payer system that would not require raising taxes on middle class families.

Some voters said they were relieved to hear Warren articulate a plan to pay for health care without tax increases that would target them. But there are signs that concerns remain beyond costs — voters who worry over everything from the plan’s political viability to its echoes of socialism. In a question-and-answer session with Warren at a town hall, a voter in Vinton who said she had Type 1 diabetes told Warren she was worried about getting continuity of care in the transition period as Medicare for All took full effect.