From the piece:
Not unconditional surrender, of course. Roy and Holtz-Eakin are conservatives who want to reduce spending, so they favor making the subsidies less generous. In order to make less generous subsidies viable, they want to loosen the regulations to make the insurance plans stingier. They want to gradually-but-steadily raise the eligibility age for Medicare, so that over time a larger-and-larger share of the elderly population will be covered by Obamacare rather than Medicare. Last, and by no means least, they want to transition low-income Americans out of Medicaid and into the Obamacare exchanges. If you did all that stuff, then you wouldn't need as much tax revenue to finance Obamacare.