California voters watch President Trump’s congressional address on television at Acme Bar & Company in Berkeley on Tuesday.

Ruy Teixeira’s new book is “The Optimistic Leftist: Why the 21st Century Will Be Better Than You Think.”

Is Donald Trump the end for the left? Is it really possible, as a baby boomer averred in an interview last month with The Washington Post, that “all the things we cared about for the past 40 years could be wiped out in the first 100 days”?

American leftists are not known for their optimism, and yet, even for them, the prevailing sentiment is that these are especially dark days. Nearly two-thirds of Democrats say they are “worried or pessimistic” about the future of the country in a new Wall Street Journal-NBC News poll.

Historian Jeremi Suri, writing in the Atlantic, assessed that “with his barrage of executive orders, Trump is taking America back to the historical nightmares of the world before December 1941: closed borders, limited trade, intolerance to diversity, arms races, and a go-it-alone national race to the bottom.” Rep. Luis Gutiérrez (D-Ill.) spoke out against Trump’s attorney general pick, saying, “If you have nostalgia for the days when blacks kept quiet, gays were in the closet, immigrants were invisible and women stayed in the kitchen, Senator Jefferson Beauregard Sessions is your man.” Climate scientists offer a similarly bleak view, fearing that Trump will quickly unravel President Barack Obama’s legacy and that “the world, then, may have no way to avoid the most devastating consequences of global warming, including rising sea levels, extreme droughts and food shortages, and more powerful floods and storms,” as the New York Times put it.

But fears that Trump will set back the left’s agenda dangerously and irreparably are not well founded. Core advances can’t be undone. Although Trump could do some real temporary damage, he and his movement will fade, and the values and priorities of the left will eventually triumph.

Consider social equality and tolerance, where some of today’s greatest fears are concentrated. It is true that Trump has said many egregious things, like associating Mexican immigrants with criminal behavior, and has tried (though so far failed) to implement a ban on immigration from some Muslim countries. But people should not lose sight of the massive progress in the past half-century, led by the left. This includes the destruction of formal and many normative barriers to racial equality, the rise of the black middle class, the advancement of women in higher education and the professions, the dominance of anti-sexist views in public opinion, and the acceptance of gays, including the institution of same-sex marriage. We still have far to go in the attainment of full social equality, but it is also true that we have gone far.

Public-opinion data is quite clear that the United States has become more, not less, liberal in all these areas over time and that these trends are continuing. Take the standard question about whether immigration levels should increase, decrease or stay the same. The 38 percent of people who say “decrease” is about as low as it ever has been since Gallup started tracking the question in the 1960s. The current number represents a massive drop, of about 30 points, since the early 1990s, when Pat Buchanan first raised his pitchfork high at the Republican National Convention. There has also been a considerable change in views about whether immigration is a good or bad thing for America — and it’s positive, not negative, change, even if one confines the data to white Americans. According to Gallup, the “good thing” response by whites was as low as 51 percent in the early 2000s but has been around 70 percent in the past two years.

Nor has there been any kind of spike in negative racial attitudes in recent years — in fact, according to the University of Chicago’s General Social Survey , such attitudes were far more prevalent in the early 1990s than they are today, including among white Democrats and Republicans. This is true even as perceptions of the quality of race relations have been dimming, thanks primarily to conflict around police shootings and to a tiny minority of genuine haters whose rhetoric and actions have been widely covered. But the underlying trend toward racial liberalism continues.

So the idea that Trump will somehow successfully relitigate the role of immigrants, minorities, gays and women in American society is scary but absurd. He may continue the Republican campaign to restrict voting rights. He may seek to overturn Roe v. Wade (supported by 70 percent of the American public). He may promote prejudice against Muslim Americans. Such actions may in fact be cheered on by his hard-core supporters. But he will ultimately fail, because what he wishes to do is both massively unpopular and runs against the grain of legal precedent and institutional norms.

And he can’t hold back the one true inevitability in demographic change: the replacement of older generations by newer ones. Underappreciated in November’s election was the continuing leftward lean of young voters, once again supporting the Democratic candidate by around 20 points — and with younger millennials, including both college-educated and noncollege whites, even more pro-Democratic than older ones. That is huge. And don’t expect these voters to shift right as they age. Political science research shows that early voting patterns tend to stick.

Another locus of disquiet, if not hysteria, on the left is the environment. But consider this: In 1969, the Cuyahoga River in Cleveland caught fire; in 1979, when Obama was attending college in Los Angeles and remembers constant smog, there were 234 days when the city exceeded federal ozone standards. Our water and air are now orders of magnitude cleaner than they were back then.

Trump will not be able to suddenly wipe out all these gains. Sure, he says he will severely cut environmental regulations, especially ones put in place by Obama; hollow out the EPA; somehow bring back the coal industry; and much more. But saying and doing are two different things. Getting rid of Obama-era rules such as the Clean Power Plan would take years and be challenged by litigation. Reversing the decline of the coal industry is economically impossible. Abolishing the EPA and gutting the clean air and water acts is politically impossible. When the George W. Bush administration tried to eliminate one Clinton-era rule on levels of arsenic in drinking water, it ran into a political buzzsaw and had to retreat.

The left’s priority of a clean environment with clean air and water is immensely popular, with deeply entrenched programs and practices that sustain it. Trump will be able to slow down environmental advances, by chipping away at relatively obscure regulations and reducing enforcement, but he cannot reverse them.

Nor will Trump be able to derail the remarkable progress on another cherished goal of the left: a green economy that can stave off global warming. The key here is abundant, cheap, clean energy, and work toward that goal has been going forward at a breakneck pace. World investments in clean energy, chiefly wind and solar, have reached levels that are double those for fossil fuel. Renewables now provide half of all new electric capacity around the world. The cost of solar has fallen to 1/150th of its 1970s level, and the amount of installed solar capacity has increased a staggering 115,000 times. Indeed, it is increasingly common for clean energy in some areas to be fully cost-competitive with fossil fuels. Trump will not and cannot stop this trend.

Or take living standards and the middle class, where progress has admittedly been slow (though not absent) in the recent past. Capitalism is certainly capable of performing much better — but Trump is not the man to make that happen. All he’s going to succeed in doing is blowing up one of the main roadblocks to better economic performance: the conservative Republican anti-government, quasi-libertarian consensus around economic policy. A protectionist president who proposes to spend $1 trillion on infrastructure, criticizes corporate decisions on job location, and swears to oppose any and all Social Security and Medicare cuts is miles away from that consensus, even if he does support slashing taxes for the rich and undermining unions. He is on a collision course with his own Congress that will result in incoherent economic policy with little or no benefit to the working-class voters who elected him.

Finally, consider the tremendous progressive achievements of the Obama era, from a stimulus bill that saved the economy and poured money into clean-energy investments to the Dodd-Frank act regulating the financial sector to the Affordable Care Act and much more. These were remarkable gains for the left, attained despite severe headwinds in the aftermath of the Great Recession.

Of course, Trump and the Republican Congress have declared their intention to roll back these advances and then some. The president has already signed executive orders that seek to weaken Dodd-Frank and undermine the ACA. But can Trump and his GOP allies really get rid of these programs, as opposed to nibbling at their edges? It will not be as easy as they expect and as many on the left fear.

The chaos surrounding Republican efforts to “repeal and replace” the Affordable Care Act illustrates just how difficult this rollback would be. The idea of repealing the ACA first and coming up with a replacement later died quickly, forcing Republicans to confront the fact that they cannot agree on what the new plan should be. Some want to keep the Medicaid expansion, some balk at requiring higher deductibles, some worry about reducing subsidies, and many fear political damage from throwing millions of people off health insurance. The disunity of the repeal forces is so palpable that former House Speaker John Boehner, who once led the charge to repeal the ACA, now admits that repeal is “not going to happen” and that “most of the framework of the Affordable Care Act” will remain in place.

Trump and the Republican Congress fail to understand, and the left would do well to remember, one of the most enduring features of American public opinion. The dominant ideology in the United States is one that combines “symbolic conservatism” (honoring tradition, distrusting novelty, embracing the conservative label) with “operational liberalism” (wanting government to take more action in a wide variety of areas). As political scientists Christopher Ellis and James Stimson, the leading academic analysts of American ideology, note: “Most Americans like most government programs. Most of the time, on average, we want government to do more and spend more. It is no accident that we have created the programs of the welfare state. They were created — and are sustained — by massive public support.”

That’s why, now that the ACA has delivered concrete benefits for many people, it is so very hard to get rid of. As a constituent of Sen. Chuck Grassley (R-Iowa) put it: “I’m on Obamacare. If it wasn’t for Obamacare, we wouldn’t be able to afford insurance. With all due respect, Sir, you’re the man that talked about the death panel. We’re going to create one great big death panel in this country if people can’t afford to get insurance.” In the long run, it is far more likely that the ACA will be built upon and improved, so that it extends coverage and tamps down rising medical costs even further (that will be the “something terrific” Trump has talked about), than truly be eliminated.

The Trump administration could still do some real damage. There will be lax enforcement of financial and environmental regulations. There will probably be tax cuts for the rich and underfunding of important social programs. There will be more harassment of immigrants and no progress on comprehensive immigration reform. But its ability to remake America in the libertarian image (privatize Social Security! voucherize Medicare!) envisioned by Paul Ryan is distinctly limited — even assuming that Trump backs such moves wholeheartedly, which he very well might not, given his public pronouncements on these programs.

In the end, the Trumpian populism of the 2010s will probably have no more staying power than the agrarian populism of the 1880s and 1890s, which was also driven by demographic groups on the decline and was similarly undercut by structural change and the transition to a new economic era. That earlier populist era was followed by an era of strong social advancement in the early 20th century — the Progressive Era.

What will have staying power in the 21st century is the values and priorities of the left. They will not win every battle, but they will win the war.