Most Americans, including myself, are not very familiar with the horde of likely 2020 Democratic presidential candidates. The debates will play a huge role in separating the sheep from the goats.
Presidential debates, particularly if they involve large numbers of people, are not a forum for nuance and tradeoffs; they reward candidates with simple solutions and zippy zingers.
When you apply that to the various options for single-payer, you have a potential problem. My fear is that the most extreme versions, which promise the moon and the stars and suggest that rich people will pay for almost all of it, will drive out the more responsible and balanced alternatives, simply because they will be easier to understand.
There are significant conceptual and political issues with single-payer that have the potential to turn into a nightmare for the Democrats in the 2020 general election. If they are not handled properly, they could win the election for Trump. More on that during the next two days.