I guess we are getting glimpses of Barack Obama's post-presidency occupation - research and publishing scientific papers in academic journals. He publishes his most technical argument for ACA in the Journal of the American Medical Association.
Of course, no one is thinking that this will change minds of Republicans who oppose ACA since we are dealing here with a mindset of medieval Roman Catholic Church which put Galileo to inquisition. Vatican took over 4 centuries to apologize to Galileo, I guess so far as Republican Party turning around ACA; we might be talking similar timescale provided Donald Trump does not burn down the GOP House in 2016.
Political case for the paper seems to be motivating Bernie Sanders voters. Bernie promised 'public option', Hillary is indicating that she will come around on that policy prescription too; hence it is logical that Obama lays down the case for 'public option' as the next phase of continued health care reforms.
With House expected to stay with Paul Ryan, there is very little chance of any positive enhancements to ACA. Best course will be for Hillary to hold the fort. Only when Democratic Base comes out in droves, there are chances that Hillary may get the mandate needed to undertaken any substantive reforms. For the infamously lethargic Democratic Base to turn out in 2016 if it means a sitting president finds time to organize a scientific paper for an academic publication, it is all worth trying.