The Biden campaign deserves praise for introducing, at the Democratic National Convention, something we haven’t seen a lot of lately — smiles. They’ve showcased grins and joyful, dancing eyes on the faces of all sorts of Americans. Sure, it’s corny. I don’t care.

Of course, we didn’t arrive at this moment of bitter polarization overnight, and we won’t be able to transcend it with one election. But the Biden team seems to be betting that many of us are yearning for a giant step toward decency.

As much as I long for national reconciliation and the pacification of our politics, I’m worried about something else — the flip side of polarization. As shrill and vicious as the discourse has become in recent years, there has also been a curious consensus emerging.

On both the left and the right, you find striking agreement that the past several decades have been a time of economic decline. Our economy, they say, is broken. We’ve been told by Sens. Elizabeth Warren and Bernie Sanders on the left, and by Donald Trump and Sen. Josh Hawley on the right, that the wealth gains of recent years have gone entirely to the top 1% of earners, that real wages for the middle class have stagnated and that the “game is rigged.”

Is the middle class in trouble? Only if you think it is bad news that, since 1967, more Americans have joined the upper-middle class. In a study published by the Brookings Institution, Stephen Rose found that the number of Americans in the upper-middle class increased from 6% in 1967 to 33% in 2016. Among African-Americans, the percentages jumped from 1% to 14% over the same period. One reason the middle class is shrinking is that more people are moving up.

Michael Strain’s new book, “The American Dream is Not Dead (But Populism Could Kill It)” is chock full of myth-busting statistics. Has the American middle class seen its wages stagnate for 30 years? No. Since 1990, the wages of typical workers (not managers or supervisors) have increased by 33%. Maybe that’s not enough, but it’s not stagnation.

Besides, some things cannot quite be captured by statistics. People used to undergo surgery and be sidelined for months with stomach ulcers. And more than 90% of homes have air conditioning today compared with 60% in 1980.

The populists of right and left have agreed on something that just isn’t so. The death of the American Dream has been vastly exaggerated. And to the extent that they’ve persuaded large numbers of Americans that our problems are those of foreigners taking our jobs or greedy 1-percenters hoarding all the gains for themselves, we are diverted from addressing our true challenges. Male labor force participation has been dropping for many years. The way we price health care is opaque and frankly, borderline insane. Child poverty is rising, in part due to the rise of single-parent families. Our schools are inadequate, deaths of despair are on the rise, racial discrimination remains a problem, and our national debt is out of control.

We have enough on our national plate without talking ourselves into the false belief in a broken economy that benefits only the rich.

Mona Charen is a senior fellow at the Ethics and Public Policy Center.