Presidential campaigns are invariably expressions of hope for the future. This is true whether the candidate is proposing continuity ("Morning in America") or change ("The Audacity of Hope"). It's even true when the candidate constantly denounces the "disaster" of the present, as Donald Trump did in 2016. Trump's message was that, however terrible things might be, he alone could fix it. America would be great again very soon.

It's therefore perfectly predictable that the busload of Democrats already running to replace Trump in 2020 would combine attacks on the racism, xenophobia, and corruption of the Republican Party with effusions of optimism along with a tidal wave of ambitious policy proposals to help turn the country around. That's how democratic politics is done.

But those of us who aren't angling to spend the next 19 months running for the nation's highest office can afford a little more honesty. The United States is a nation facing problems far more daunting than any candidate for high office can admit or acknowledge. It falls to the rest of us to face that reality forthrightly and without denial.

Let's start with the obvious: Just over two years ago, a democratic election combined with institutions designed more than two centuries ago delivered the presidency to an ignoramus who leads a party utterly lacking a concept of the public good. (The GOP believes in a fantasy that the public good takes care of itself when the wealthiest private citizens and corporations pursue maximal profits for themselves.)

To cite just the latest example (there's a new one every few days), congressional Republicans voted dozens of times during the Obama administration to repeal the Affordable Care Act. Once the party gained control of Congress and the White House, which gave them the chance to follow through, they fell short — because they could reach no consensus on an alternative. Yet that hasn't stopped President Trump from trying again to scuttle it, this time through a transparently frivolous lawsuit. That there is nothing approaching an alternative in the works doesn't faze the president one bit, even though it would summarily end health insurance coverage for many millions of Americans — no doubt in part because he and his chief of staff are content to lie flagrantly about the near-certain consequences of their actions.

Such priorities and behavior are very good reasons to support the Democrats as an alternative. The Democratic candidates are proposing a long list of appealing policies that would begin to address some of our biggest problems — universal health coverage, free college, universal child care, massive spending to combat climate change, and much else. That sounds good, except that, if implemented, these policies would bankrupt the country.

The federal government is already running the largest peacetime deficits in American history, and it's doing so during an economic boom, when tax revenue should be at its highest point in the business cycle. Raising upper-income taxes, imposing a wealth tax, cutting defense spending, repealing Trump's corporate tax cut — all of it would offset some (though only some) of the spending Democrats are advocating. But those changes would likely also produce an economic slowdown that would lead to a decline in tax revenue.

In response to this obvious objection, some on the left have begun to tout something called Modern Monetary Theory, which is the progressive version of the right-wing fantasy of the public good taking care of itself through the profit-seeking of the wealthy. In this alternative fantasy, the government is free to spend as much as it wants on public goods, without regard for deficits or the consequences of massive debt (above all, the risk of hyperinflation).

But let's leave that aside and imagine for the sake of argument that one of the most ambitious Democrats wins in 2020, is swept into power with substantial enough congressional majorities to get a radical agenda enacted, isn't confronted by a right-wing reaction that culminates in civil violence, and doesn't immediately face economically crippling budget deficits. Even in that rosiest scenario, a daunting list of problems would remain unaddressed.

The country's infrastructure — roads, bridges, railways, levees — is collapsing. Life expectancy is falling, in large part because so many Americans are addicted to painkillers. Manufacturing jobs have disappeared. Automation is on track to eliminate many more low-skill jobs, leaving millions of Americans out of work. Communities across wide swaths of the country are cultural wastelands with few economic prospects, while restrictive zoning laws in regions with high rates of economic growth ensure that housing costs are prohibitively high, leaving people overworked and financially strapped.

The challenges are daunting, the resources to address them are limited, and our capacity to reach anything approaching a consensus about how to begin doing so is close to impossible. I suspect this is one important reason why a majority of Americans have consistently described the country as on the wrong track for the past 15 years — before the financial crisis, during its extended aftermath, and on through a period of extensive, sustained growth that's brought unemployment down to historic lows. We sense, rightly, that we've neglected our problems for so long that the capacity to fix them may well exceed our grasp.

It's no surprise that presidential aspirants refrain from talking this way. They have a product to sell, and you don't sell anything by looking and sounding downcast.

The honest truth is that these days the American future often feels uncertain and sometimes downright grim. That doesn't mean turning things around is impossible. The U.S. made it through the tumult of industrialization over a century ago to reach unprecedented heights. Perhaps several decades from now we will look back on the opening decades of the 21st century the way we now view the turn of the 20th century — as a moment of temporary turbulence on the way to renewed national achievement.

But it's also possible that we've passed our zenith and entered what will be a long period of national decline. It may be too soon to expect our politicians to acknowledge and respond productively to this possibility. But it won't be forever. Sooner or later, we will have to give up our fantasies and confront the world as it is. Even if it fails to conform to our most fervent hopes.