Donald Trump said on Monday that he wanted to usher in “economic renewal,” but most of his proposals would hurt the economy, rack up huge deficits, accelerate climate change and leave the country isolated from the world.

In a speech billed as a blueprint for stimulating growth and creating jobs, Mr. Trump offered a grab bag of ideas that borrow from discredited supply-side economics, the fossil fuel industry’s wish list and “America First” isolationism. He also criticized Hillary Clinton and President Obama for what he called their “job-killing, tax-raising, poverty-inducing” agenda. It was vintage Trump, full of promises of greatness and victories backed by fantastical proposals.

Mr. Trump told the Detroit Economic Club that he would cut taxes to an extent not seen since Ronald Reagan was in the White House. He said he would slash the corporate tax rate to 15 percent, arguing that the current statutory 35 percent is one of the highest among developed countries. He did not mention that the average effective corporate tax rate was 18.1 percent in 2015, including state and local taxes, according to the White House and the Treasury Department. He claims he would help workers by getting rid of the estate tax, though repealing it would have almost no effect on working families. Under current law, that tax doesn’t touch 99.8 percent of all estates because it applies only to that portion of an estate that exceeds $5.4 million for an individual or $10.9 million for a married couple.

The big problem with Mr. Trump’s tax ideas is that they would leave a multitrillion-dollar deficit for no benefit. Proponents of supply-side economics argue that cutting tax rates encourages people to work and businesses to invest. But the gains are much more modest than proponents claim because many businesses won’t invest unless demand for their products is growing and many people are not motivated by lower tax rates to work more.
On the other hand, significant tax cuts exact very real costs. Mr. Trump’s previous tax plan, released last year, would have reduced federal revenue by $9.5 trillion over 10 years, according to the Tax Policy Center, meaning that Mr. Trump would have to slash government spending or increase borrowing substantially. George W. Bush pushed big tax cuts through Congress in 2001 and 2003 with the promises of strong growth that never materialized.

Shaken by a failed coup attempt, Turkey’s government and many of its citizens are desperate for someone to blame. Instead of undertaking a thorough investigation of the facts, though, they have accused the United States of complicity in the insurrection. This has ignited a new wave of anti-Americanism that, combined with a sweeping government crackdown against enemies real and imagined, poses a serious risk to NATO, relations with the United States and Turkey’s long-term stability.

The main culprit behind the July 15 coup, according to President Recep Tayyip Erdogan and other Turkish leaders, is Fethullah Gulen, a Muslim cleric who has lived in self-imposed exile in Pennsylvania since 1999 and has denied any involvement in the attempted overthrow. But the pro-government press, political leaders and ordinary citizens across all segments of society are also pointing fingers at Washington, which has denied any involvement.

When Gen. Joseph Votel, the top American commander in the Middle East, told a security conference last week of his concerns about the effect of the purge on Turkish officers, including some who worked with the Americans and are now jailed, Mr. Erdogan faulted him for taking “the side of the coup plotters.” On Tuesday, Mr. Erdogan kept at it, giving a speech in which he said that in standing by the putschists, the West supported “terrorism.”

The sweeping purges and mass arrests since last month’s failed military coup in Turkey have confirmed many of the worst fears about President Recep Tayyip Erdogan’s government. They are the most recent in a long history of abuses. Over the last few years, Mr. Erdogan has harshly repressed the Turkish press and civil society, supported extremist militant groups in Syria, broken off a promising peace process with his country’s Kurdish nationalists, and worked relentlessly to change his country’s Constitution so he can rule as a quasi-dictator.

From Washington’s point of view, Turkey has become as much of a headache as an ally. Never has a NATO member strayed so far from the fold. This pushes the United States toward a painful choice. It can disavow Mr. Erdogan, break with Turkey and even try to expel it from NATO. That would be the moral course toward a tyranny-in-the-making. It would also bring coherence back to NATO policy in Syria, where today one ally, the United States, supports factions that another ally, Turkey, attacks and bombs.

The alternative is to swallow hard, recognize Turkey’s unique geopolitical importance and accept Mr. Erdogan as he is. This is the messier and less noble option, but the likelier one because it best suits American interests. Turkey is heading toward international isolation — and perhaps even economic crisis and civil war. To cast it loose at this moment would be to renounce Washington’s remaining influence in Ankara, which is substantial. It would also be an abandonment of its many Turkish friends, the millions who mourn the erosion of democracy and may have the chance to rebuild it when this dark era is past.

When Donald Trump began his run for the White House, many people treated it as a joke. Nothing he has done or said since makes him look better. On the contrary, his policy ignorance has become even more striking, his positions more extreme, the flaws in his character more obvious, and he has repeatedly demonstrated a level of contempt for the truth that is unprecedented in American politics.

Yet while most polls suggest that he’s running behind in the general election, the margin isn’t overwhelming, and there’s still a real chance that he might win. How is that possible? Part of the answer, I’d argue, is that voters don’t fully appreciate his awfulness. And the reason is that too much of the news media still can’t break with bothsidesism — the almost pathological determination to portray politicians and their programs as being equally good or equally bad, no matter how ludicrous that pretense becomes.

Just to be clear, I’m not arguing that distorted news coverage is the whole story, that nobody would support Trumpism if the media were doing their job. The presumptive Republican nominee wouldn’t have gotten this far if he weren’t tapping into some deep resentments. Furthermore, America is a deeply divided country, at least in its political life, and the great majority of Republicans will support their party’s nominee no matter what. Still, the fact is that voters who don’t have the time or inclination to do their own research, who get their news analysis from TV or regular news pages, are fed a daily diet of false equivalence.

Donald Trump gave a speech on economic policy last week. Just about every factual assertion he made was wrong, but I’m not going to do a line-by-line critique. What I want to do, instead, is talk about the general thrust: the candidate’s claim to be on the side of American workers.

Of course, that’s what they all say. But Trumponomics goes beyond the usual Republican assertions that cutting taxes on corporations and the rich, ending environmental regulation and so on will conjure up the magic of the marketplace and make everyone prosper. It also involves posing as a populist, claiming that getting tough on foreigners and ripping up our trade agreements will bring back the well-paying jobs America has lost.

That’s a departure, although not as much as you may think — people forget that Mitt Romney similarly threatened a trade war with China during the 2012 campaign. Still, it was interesting to see a Republican presidential candidate name-check not just Bernie Sanders but the left-leaning Economic Policy Institute, which has long been critical of globalization.

But the institute is having none of it: Lawrence Mishel, the think tank’s president, put out a derisive reply to what he called the “Trump trade scam.” His point was that even if you think, as he does, that trade agreements have hurt American workers, they’re only part of a much broader set of anti-labor policies. And on everything else, Donald Trump is very much on the wrong side of the issues.

About globalization: There’s no question that rising imports, especially from China, have reduced the number of manufacturing jobs in America. One widely-cited paper estimates that China’s rise reduced U.S. manufacturing employment by around one million between 1999 and 2011. My own back-of-the-envelope calculation suggests that completely eliminating the U.S. trade deficit in manufactured goods would add about two million manufacturing jobs.

But America is a big place, and total employment exceeds 140 million. Shifting two million workers back into manufacturing would raise that sector’s share of employment back from around 10 percent to around 11.5 percent. To get some perspective: in 1979, on the eve of the great surge in inequality, manufacturing accounted for more than 20 percent of employment. In the 1960s it was more than 25 percent. I’m not sure when, exactly, Mr. Trump thinks America was great, but Trumponomics wouldn’t come close to bringing the old days back.

Do you remember what happened when the Berlin Wall fell? Until that moment, nobody realized just how decadent Communism had become. It had tanks, guns, and nukes, but nobody really believed in its ideology anymore; its officials and enforcers were mere careerists, who folded at the first shock.

It seems to me that you need to think about what happened to the G.O.P. this election cycle the same way.

The Republican establishment was easily overthrown because it was already hollow at the core. Donald Trump’s taunts about “low-energy” Jeb Bush and “little Marco” Rubio worked because they contained a large element of truth. When Mr. Bush and Mr. Rubio dutifully repeated the usual conservative clichés, you could see that there was no sense of conviction behind their recitations. All it took was the huffing and puffing of a loud-mouthed showman to blow their houses down.

But as Mr. Trump is finding out, the Democratic establishment is different.

As some political scientists are now acknowledging, America’s two major parties are not at all symmetric. The G.O.P. is, or was until Mr. Trump arrived, a top-down hierarchical structure enforcing a strict, ideologically pure party line. The Democrats, by contrast, are a “coalition of social groups,” from teachers’ unions to Planned Parenthood, seeking specific benefits from government action.

This is not a column about Donald Trump.

It’s not about the fraudulent scheme that was Trump University. It’s not about his history of failing to pay contractors, leading to hundreds of legal actions. It’s not about how he personally profited while running his casinos into the ground. It’s not even concerned with persistent questions about whether he is nearly as rich as he claims to be, and whether he’s ever done more than live off capital gains on his inheritance.

No, my question, as Democrats gleefully tear into the Trump business record, is why rival Republicans never did the same. How did someone who looks so much like a cheap con man bulldoze right through the G.O.P. nomination process?

I mean, it’s not as if any of this dirt was deeply hidden. The Trump U. story was out there long before it became the big deal it is today. It took some real reporting to flesh out the details of Mr. Trump’s other business practices, but we’re talking about ordinary if skillful journalistic legwork, not revelations from Deep Throat.

So why didn’t any of Mr. Trump’s primary opponents manage to make an issue of his sleazy business career? Were they just incompetent, or is there something structural about the modern Republican Party that makes it unable to confront grifters?

The answer, I’d argue, is the latter.

On Tuesday the political arm of the Natural Resources Defense Council, one of America’s most influential environmentalist groups, made its first presidential endorsement ever, giving the nod to Hillary Clinton. This meant jumping the gun by a week on her inevitable designation as the presumptive Democratic nominee, but the NRDC Action Fund is obviously eager to get on with the general election.

And it’s not hard to see why: At this point Donald Trump’s personality endangers the whole planet.

We’re at a peculiar moment when it comes to the environment — a moment of both fear and hope. The outlook for climate change if current policies continue has never looked worse, but the prospects for turning away from the path of destruction have never looked better. Everything depends on who ends up sitting in the White House for the next few years.

On climate: Remember claims by climate denialists that global warming had paused, that temperatures hadn’t risen since 1998? That was always a garbage argument, but in any case it has now been blown away by a series of new temperature records and a proliferation of other indicators that, taken together, tell a terrifying story of looming disaster.

At the same time, however, rapid technological progress in renewable energy is making nonsense — or maybe I should say, further nonsense — of another bad argument against climate action, the claim that nothing can be done about greenhouse gas emissions without crippling the economy. Solar and wind power are getting cheaper each year, and growing quickly even without much in the way of incentives to switch away from fossil fuels. Provide those incentives, and an energy revolution would be just around the corner.

So we’re in a state where terrible things are in prospect, but can be avoided with fairly modest, politically feasible steps. You may want a revolution, but we don’t need one to save the planet. Right now all it would take is for America to implement the Obama administration’s Clean Power Plan and other actions — which don’t even require new legislation, just a Supreme Court that won’t stand in their way — to let the U.S. continue the role it took in last year’s Paris agreement, guiding the world as a whole toward sharp reductions in emissions.

In general, you shouldn’t pay much attention to polls at this point, especially with Republicans unifying around Donald Trump while Bernie Sanders hasn’t conceded the inevitable. Still, I was struck by several recentpolls showing Mr. Trump favored over Hillary Clinton on the question of who can best manage the economy.

This is pretty remarkable given the incoherence and wild irresponsibility of Mr. Trump’s policy pronouncements. Granted, most voters probably don’t know anything about that, in part thanks to substance-free news coverage. But if voters don’t know anything about Mr. Trump’s policies, why their favorable impression of his economic management skills?

The answer, I suspect, is that voters see Mr. Trump as a hugely successful businessman, and they believe that business success translates into economic expertise. They are, however, probably wrong about the first, and definitely wrong about the second: Even genuinely brilliant businesspeople are often clueless about economic policy.

An aside: In part this is surely a partisan thing. Over the years, polls have generally, although not universally, shown Republicans trusted over Democrats to manage the economy, even though the economy has consistently performed better under Democratic presidents. But Republicans are much better at promoting legends — for example, by constantly hyping economic and jobs growth under Ronald Reagan, even though the Reagan record was easily surpassed under Bill Clinton.

Back to Mr. Trump: One of the many peculiar things about his run for the White House is that it rests heavily on his claims of being a masterful businessman, yet it’s far from clear how good he really is at the “art of the deal.” Independent estimates suggest that he’s much less wealthy than he says he is, and probably has much lower income than he claims to have, too. But since he has broken with all precedents by refusing to release his tax returns, it’s impossible to resolve such disputes. (And maybe that’s why he won’t release those returns.)

Remember, too, that Mr. Trump is a clear case of someone born on third base who imagines that he hit a triple: He inherited a fortune, and it’s far from clear that he has expanded that fortune any more than he would have if he had simply parked the money in an index fund.

But leave questions about whether Mr. Trump is the business genius he claims to be on one side. Does business success carry with it the knowledge and instincts needed to make good economic policy? No, it doesn’t.

THE first tweet arrived as cryptic code, a signal to the army of the “alt-right” that I barely knew existed: “Hello ((Weisman)).” @CyberTrump was responding to my recent tweet of an essay by Robert Kagan on the emergence of fascism in the United States.

“Care to explain?” I answered, intuiting that my last name in brackets denoted my Jewish faith.

“What, ho, the vaunted Ashkenazi intelligence, hahaha!” CyberTrump came back. “It’s a dog whistle, fool. Belling the cat for my fellow goyim.” With the cat belled, the horde was unleashed.

The anti-Semitic hate, much of it from self-identified Donald J. Trump supporters, hasn’t stopped since. Trump God Emperor sent me the Nazi iconography of the shiftless, hooknosed Jew. I was served an image of the gates of Auschwitz, the famous words “Arbeit Macht Frei” replaced without irony with “Machen Amerika Great.” Holocaust taunts, like a path of dollar bills leading into an oven, were followed by Holocaust denial. The Jew as leftist puppet master from @DonaldTrumpLA was joined by the Jew as conservative fifth columnist, orchestrating war for Israel. That one came from someone who tagged himself a proud future member of the Trump Deportation Squad.

The imaginings by my tormentors of me as an Orthodox Jew in wide-brimmed hat and Hasidic garb were, of course, laughable. The truth is, I have become largely disconnected from Jewish life and faith over the years, and like many American Jews I have been lulled into complacency. Our politics have dispersed between the parties. Our coreligionists grace our movie screens, lead the cities of Los Angeles and Chicago, help oversee the Senate Intelligence Committee, succeed without apology, but also struggle like everyone else.