What makes anyone think that there isn't a way to overrule Single Payer?
The best way to campaign on a single payer platform would be "expand Medicare" to everyone. No backroom deals and all the bs that went into ACA.
All one has to do is expand the payroll tax to fund Medicare for all. I see little chance of that being overturned. The catch would be to campaign on that tax hike. ACA was constructed to avoid any overt tax hikes, to the extent of the confusion in court this week as to its status as a tax vs a penalty.