Those comments echoed what he wrote in a recent column for the New England Journal of Medicine. While conceding that changes in political leadership naturally lead to different approaches to policy, he pleaded with Republicans to think carefully about the implications of a repeal plan that he framed as purely political.

"What the past 8 years have taught us is that health care reform requires an evidence-based, careful approach, driven by what is best for the American people. That is why Republicans' plan to repeal the ACA with no plan to replace and improve it is so reckless. Rather than jeopardize financial security and access to care for tens of millions of Americans, policymakers should develop a plan to build on what works before they unravel what is in place," he wrote.

While Congressional Republicans and Trump are nominally united in support of repealing the ACA, they have yet to agree on how to proceed with their stated "repeal and replace" plan.

While Trump has suggested he wants a plan that ensures coverage for the millions who have gained it through the ACA, other Republicans, such as Sen. Rand Paul, R-Ky., have argued that the party should not make those types of promises, which they do not view as the responsibility of the federal government.

Meanwhile, some GOP leaders have argued for a "repeal and delay" strategy, by which the ACA repeal does not go into effect for several years while Congress comes up with a replacement. That strategy, however, is being attacked by both Democrats and some Republicans who view it as essentially conceding to the public that the party doesn't have a better health care plan ready.

Democrats, including the outgoing president, are hoping to exploit these divisions within the GOP as they attempt to stop an Obamacare repeal from making it through the Senate, where the GOP is operating with only a four-seat majority. If just three of the 52 Senate Republicans are unwilling to support the repeal bill, it is dead.