Barack Obamas two largest achievements during his presidencys 70 percent of the second decade altered the publics thinking and the governments functioning. When he entered office, there was only a moderate consensus, but when he left it was decisive, that everyone should have health-care coverage and that this should not be denied because of preexisting health conditions.

Obamas largest impact on governance was the expansion of Medicaid under the ACA. This has addicted 36 so far state legislatures and the District of Columbia on a large flow of federal funds. Those 37 jurisdictions, with 64 percent of the nations population (and soon perhaps Oklahoma and Missouri, both of which may have a ballot measure on expansion in 2020), are especially, and irrevocably, enmeshed in ever-deepening government supervision of health care. The American economys health-care sector is larger than all but three other nations entire economies, and as this decade ends, so does the sterile debate framed as a binary choice between government and private provision of health care. This is a blurred distinction without a clear difference.

Beginning in 2010, the Republican Partys defining its only important domestic policy was to repeal and replace the ACA. Now it is clear, probably even to the declining number of Republicans who continue to substitute that chant for thought, that this will not happen. Regarding health care, the partys intellectual pantry is now almost empty. Louisiana Sen. Bill Cassidy and a few others are working on restocking it. Perhaps they can dilute the partys current dreadful purity as a cult of personality.

In 2019, the Democratic presidential candidates debates about health care have perhaps presaged a healthier party in 2020. The beginning of T.S. Eliots East Coker In my beginning is my end could be Sen. Kamala D. Harriss campaigns autopsy. Five months before she had the kamikaze courage to embrace the most futile and despised social policy of the last third of the previous century compulsory busing of schoolchildren away from their neighborhood schools, in pursuit of racial balance Harris did something even less explicable. Seven days after her campaign began, with a flippancy that proclaimed her unfamiliarity with health cares complexities, she essentially said: Come to think about it, or actually without really thinking about it, lets move on from private health insurance. Has any presidential campaign begun by alarming more people?

Sen. Elizabeth Warrens presidential prospects may have passed their apogee on Nov. 1, when she explained, or purported to explain, how she would pay for her version of Medicare-for-all. Various analysts of different philosophic persuasions came to the same conclusion: She fell $10 trillion or so short of the real one-decade cost of her single-payer plan. In 2016, Hillary Clinton said a single-payer plan would never, ever come to pass. Warrens only concession to reality has been to promise to not implement her plan until three years after she has fulfilled her recent promise she cannot moderate her aggressions against those who disagree with her to wear a Planned Parenthood scarf at her inauguration.

In 2016, Donald Trump lost the popular vote by 2,833,224, which was 521,366 more than the combined margins of victory of John F. Kennedy in 1960 (118,574), Richard M. Nixon in 1968 (510,314) and Jimmy Carter in 1976 (1,682,970). But in 2020, as in 2016, Trumps political strategy will be to reach Election Day as only the second-most-unpopular politician in the country. If he succeeds, he might owe his tattered success to the other partys combination of ignorance and arrogance regarding health care.

In 1993, as Bill Clintons administration arrived jauntily promising a root-and-branch remaking of a health-care sector less complex than todays, Sen. Daniel Patrick Moynihan (D-N.Y.) was warning: Ideological certainty easily degenerates into an insistence upon ignorance. The great strength of political conservatives at this time (and for a generation) is that they are open to the thought that matters are complex. Liberals have got into a reflexive pattern of denying this.

Such denial breeds political recklessness in the deniers, dismay among voters and despair among people who know things. Next year, with the most complex domestic problem health care uppermost in many voters minds, denial might produce a presidents reelection.

Read more from George F. Wills archive or follow him on Facebook.

Read more:

Paul Waldman: Our health-care debate is a disaster. Heres how we can do better.

Megan McArdle: On health care, Warren sounded like a student who hadnt done her reading

Jennifer Rubin: The moderates health-care message can prevail

The Posts View: Democrats can be progressive and practical. Some of the candidates get that.

Megan McArdle: Hey, Democrats, why not talk about health-care delivery, not just about costs?