Three or four decades ago, the United States was the most prosperous country on earth. It had the mightiest military and the most advanced technologies known to humanity. Today, it’s still the richest, strongest and most inventive. But when it comes to the health, well-being and shared prosperity of its people, the United States has fallen far behind.

Pick almost any measure of social health and cohesion over the last four decades or so, and you will find that the United States took a wrong turn along the way.

How did we get here? How do we exit?

As the presidential campaign draws the political debate to our national priorities, these questions must take center stage. As candidates argue over the budget deficit and the national debt, debate what to do about income inequality, address the problem of mass incarceration or refight the battles over the Affordable Care Act and the minimum wage, they should be forced to address how their policy wish list adds up to an answer.

Looking at how the United States compares with other nations is illuminating. As I noted in last week’s column, over the last four decades or so, the labor market lost much of its power to deliver income gains to working families in many developed nations.

But blaming globalization and technological progress for the stagnation of the middle class and the precipitous decline in our collective health is too easy. Jobs were lost and wages got stuck in many developed countries.

What set the United States apart — what made the damage inflicted upon American society so intense — was the nature of its response. Government support for Americans in the bottom half turned out to be too meager to hold society together.

The conservative narrative of America’s social downfall, articulated by the likes of Charles Murray from the American Enterprise Institute, posits that a large welfare state, built from the time of the New Deal in the 1930s through the era of the Great Society in the 1960s, sapped Americans’ industriousness and undermined their moral fiber.