By THE EDITORIAL BOARD – The New York Times.

Barack Obama is leaving the White House with polls showing him to be one of the most popular presidents in recent decades. This makes sense. His achievements, not least pulling the nation back from the worst economic crisis since the Great Depression, have been remarkable — all the more so because they were bitterly opposed from the outset by Republicans who made it their top priority to ensure that his presidency would fail.

Many Americans celebrated the election of the first African-American president as a welcome milestone in the history of a nation conceived in slavery and afflicted by institutional racism. Yet the bigotry that president-elect Donald Trump capitalized on during his run for office confirmed a point that Mr. Obama himself made from the start: that simply electing a black president would not magically dispel the prejudices that have dogged the country since its inception. Even now, these stubborn biases and beliefs, amplified by a divisive and hostile campaign that appealed not to people’s better instincts but their worst, have blinded many Americans to their own good fortune, fortune that flowed from policies set in motion by this president.

That story begins on Inauguration Day in 2009. That’s when Mr. Obama inherited a ravaged economy that was rapidly shedding jobs and forcing millions of people from their homes. The Obama stimulus, which staved off a 1930s-vintage economic collapse by pumping money into infrastructure, transportation and other areas, passed the House without a single Republican vote. Republican gospel holds that government spending does not create jobs or boost employment. The stimulus did both — preserving or creating an average of 1.6 millions jobs a year for four years. (A timely federal investment in General Motors and Chrysler, both pushed to the brink during the recession, achieved similarly salutary results, preserving more than a million jobs.)

Mr. Obama’s opponents have had trouble accepting that any of this actually happened. They have not learned the simple truth — a truth clear in the New Deal and just as clear now — that timely and significant federal investment can make a real difference in people’s lives. Or accepted that compassionate and well-designed government programs can do the same. Driven by ideology or envy, or maybe both, Republican leaders have now pounced upon the demonstrably successful Affordable Care Act of 2010, a law that has improved the way medical care is delivered in the United States, providing affordable care for millions and driving the percentage of Americans without insurance to a record low 9.1 percent in 2015. Despite the law’s clear successes, Mr. Trump and Republican congressional leaders have nevertheless declared it a failure, hoping to justify a repeal that would rob an estimated 22 million people of health insurance. The point of following this destructive course can only be to destroy a central Obama legacy — even though doing so will drive up costs and cause havoc in the lives of the newly uninsured.

With no help from Congress, Mr. Obama has also managed to make progress on issues where nobody gave him much of a chance, notably climate change, which both he and his secretary of state, John Kerry, placed very near the top of their to-do list. Against heavy odds, Mr. Obama first managed to persuade the Chinese to join the effort. This demolished the critics’ argument that he was asking America to do all the heavy lifting. It also made possible the Paris agreement in December 2015, in which 195 nations agreed on a plan that they hope will reduce greenhouse gases that are warming the atmosphere and threatening the viability of the planet itself.

Americans will miss Mr. Obama’s negotiating skills on tough issues and the dignity and character that he and his family brought to the White House. Beyond that, they will also miss an impassioned speaker whose eloquence ranks with that of Abraham Lincoln. The way he has defended the founding precepts of the United States while also arguing that those precepts have to be broadened to achieve a new inclusiveness has been especially striking, as have his remarks delivered at moments of national tragedy.

His 2015 eulogy in Charleston, S.C., after a Confederate flag-waving white supremacist slaughtered nine African-American parishioners at Emanuel African Methodist Episcopal Church, was redolent with history. As always, he viewed the horror through the prism of a seemingly innate optimism about the country’s ability to set aside hatred and move toward a more perfect union.

Mr. Obama never would have gained the office without that unflagging optimism, which inspired a generation of young voters who saw in him a new kind of leader. So it seemed fitting that he would end his farewell address in Chicago on Tuesday with them in mind:

“Let me tell you, this generation coming up — unselfish, altruistic, creative, patriotic — I’ve seen you in every corner of the country. You believe in a fair and just and inclusive America; you know that constant change has been America’s hallmark, that it’s not something to fear but something to embrace; you are willing to carry this hard work of democracy forward. You’ll soon outnumber any of us, and I believe as a result the future is in good hands.”