A majority of Americans could not tell you the details of M4A if their lives depended on it. What a majority of Americans want is cheaper medical care and cheaper insurance. (They want lower taxes, too, with no plan for how it's financed!)
Any number of people have proposed something they call Medicare For All, and each of their proposals has different details. From single-payer (which is defined as government paying for everything necessary for everybody, financed by taxes), to existing Medicare with buy-in payments from people using a schedule of complex calculations based on age and income.
I much prefer the latter myself, and try to avoid the confusing mess by calling it UK-style National Health. I think calling it Medicare For All is a semantic ploy to make it more acceptable to most people who think: "Medicare is good, so why not Medicare for me?"
One ironic thing is that for all the progressives that criticize Bill Clinton for being a Republican-lite, the Clinton's health care proposal would have covered everybody!
