WASHINGTON — The Republican National Convention in Cleveland this week ought to be interesting, but whether it will be informative is another question. Barring a last-minute surprise, the delegates will nominate real estate magnate Donald Trump to be the GOP presidential candidate, and he will pledge — probably repeatedly — to “make America great again.”

Just how he plans to do this (or whether the slogan is simply a clever sound bite) is something of a mystery, because Trump has advanced only the sketchiest of agendas. By now, its main elements are well-known: He would evict the estimated 11 million illegal immigrants; slap stiff tariffs (35 and 45 percent) on Mexican and Chinese imports; ban Muslims from entering the U.S.; and push Congress to pass a $9.5 trillion tax cut over a decade.

It’s doubtful that this program could be enacted in its entirety. Shipping 11 million people out of the country — to take an obvious example — is, at best, a cruel and daunting logistical exercise. It would surely face legal and political challenges. But even if the full program were adopted, it wouldn’t restore America to some prior period of grandeur.

Think about it. If 11 million people left the country, there would be less spending. The economy would weaken. Likewise, production of many items made in Mexico and China would not return to the United States but would shift to other low-wage countries. There would probably be retaliation against U.S. exports to Mexico ($236 billion in 2015) and China ($116 billion), costing American jobs.

As for the massive tax cut, the economy doesn’t need more “stimulus” now. The unemployment rate is 4.9 percent. If taxes were cut anyway, or used to offset a Trump-induced recession, large budget deficits would grow still larger. (This assumes — as seems likely — that the tax cuts aren’t fully offset by spending reductions.)

None of this constitutes a plausible program for economic renewal. It’s a hodge-podge of mostly bad ideas that’s supposed to hypnotize large numbers of Americans who feel (understandably in many cases) that they’ve been misused by an economy that mainly serves a wealthy upper class. Their incomes are squeezed; their jobs are less secure.

The pledge “to make America great again” is not an economic project. It’s an exercise in mass psychology. The idea is to get people to displace their anger and frustration onto groups which (in Trump’s view) have eroded America’s “greatness” — Mexicans, Muslims, the Chinese, political and financial elites and “the media.” The Trump treatment is to peddle hatred and resentment for his political gain.

As an election strategy, this might succeed if enough people subscribe to his self-serving stereotypes. But as economic policy, it’s mostly a dud. It won’t change most people’s objective circumstances. In some cases, it may protect them from imports. But for most, it won’t provide jobs, and any income gains from tax cuts are skewed toward the rich. Sooner or later, people will recognize that they’ve been had.

Trump’s serious deficiencies are of character, not intellect. He is a salesman whose favorite product is himself. His moral code is defined by what works. What works to build his popularity is legitimate, even if it’s untrue, tasteless, personally cruel or inconsistent with what he’s said before. What doesn’t work is useless, even if it involves inconvertible truths, important policies or common courtesies.

One consequence is a paucity of genuine policy debates. Consider budget deficits. Based on current policies, the Congressional Budget Office projects that annual deficits will go from today’s 3 percent of the economy (gross domestic product) to 8 percent of GDP by the 2040s. What should be done? Trump hasn’t had much to say. (To be fair, neither has Hillary Clinton.)

There’s no secret as to what’s happening. A slowing economy is colliding with a rising demand for government benefits, driven mainly by an aging society and its impact on federal programs for the elderly. Even in 2016, Social Security and Medicare represent nearly half of non-interest federal spending. Their share will grow.

How much should we allow the expanding benefits for the elderly to degrade the rest of government — from defense to highways to subsidized school lunches — by slowly squeezing non-elderly spending? This is a central political question of our time, and it has been evaded for obvious reasons (either taxes must go up or spending must go down).

The role of campaigns and elections in democracies is to let the people speak. Ideally, it is to shape public opinion by informing it and allowing it to coalesce around widely shared beliefs. But when the information being served up is false, incomplete or deceptive, the process is perverse. It sows disillusion, not progress.

Robert Samuelson is a columnist with The Washington Post.