Earlier quoted context omitted.
It's not really outside the Overton window. Universal healthcare has strong majority support right now. Employers and shareholders benefit significantly by reducing options for workers and by making it difficult for workers to change jobs; the source of the resistance is there, in the plain language of power, not in some imaginary spectrum of what's considered to be acceptable.
Universal healthcare has decent (but not 'strong majority') support in the abstract [1]. In terms of concrete proposals (i.e. once you've answered the questions of what universal healthcare is and how you pay for it), there is not a single plan that is even somewhat popular. [1] https://fivethirtyeight.com/features/democrats-have-no-safe-...
[1] https://thehill.com/hilltv/what-americas-thinking/412545-70-...