The biggest issue facing the American economy, and our political system, is the gradual descent of the middle class into proletarian status. This process, which has been going on intermittently since the 1970s, has worsened considerably over the past five years, and threatens to turn this century into one marked by downward mobility.

The decline has less to do with the power of the “one percent” per se than with the drying up of opportunity amid what is seen on Wall Street and in the White House as a sustained recovery. Despite President Obama’s rhetorical devotion to reducing inequality, it has widened significantly under his watch. Not only did the income of the middle 60% of households drop between 2010 and 2012 while that of the top 20% rose, the income of the middle 60% declined by a greater percentage than the poorest quintile. The middle 60% of earners’ share of the national pie has fallen from 53% in 1970 to 45% in 2012.

This group, what I call the yeoman class — the small business owners, the suburban homeowners , the family farmers or skilled construction tradespeople– is increasingly endangered. Once the dominant class in America, it is clearly shrinking: In the four decades since 1971 the percentage of Americans earning between two-thirds and twice the national median income has dropped from 61% to 51% of the population, according to Pew.

Roughly one in three people born into middle class-households , those between the 30th and 70th percentiles of income, now fall out of that status as adults.

Neither party has a reasonable program to halt the decline of the middle class. Previous generations of liberals — say Walter Reuther, Hubert Humphrey, Harry Truman, Pat Brown — recognized broad-based economic growth was a necessary precursor to upward mobility and social justice. However, many in the new wave of progressives engage in fantastical economics built around such things as “urban density” and “green jobs,” while adopting policies that restrict growth in manufacturing, energy and housing. When all else fails, some, like Oregon’s John Kitzhaber, try to change the topic by advocating shifting emphasis from measures of economic growth to “happiness.”

Other more ideologically robust liberals, like New York Mayor Bill de Blasio, call for a strong policy of redistribution, something with particular appeal in a city with one of the highest levels of income inequality in the country. Over time a primarily redistributionist approach may improve some material conditions, but is likely to help create a permanent underclass of dependents, including part-time workers, perpetual students, and service employees living hand to mouth, who can make ends meet only if taxpayers subsidize their housing, transportation and other necessities.

Given the challenge being mounted by de Blasio and hard left Democrats, one would imagine that business and conservative leaders would try to concoct a response. But for the most part, particularly at the national level, they offer little more than bromides about low taxes, particularly for the well-heeled investor and rentier classes, while some still bank on largely irrelevant positions on key social issues to divert the middle class from their worsening economic plight.

The country’s rise to world preeminence and admiration stemmed from the fact that its prosperity was widely shared. In the first decades after the Second World War, when the percentage of households earning middle incomes doubled to 60%, it was no mirage, but a fundamental accomplishment of enlightened capitalism.

In contrast, the current downgrading of the middle class undermines the appeal of the “democratic capitalism” that so many conservative intellectuals espouse. In reality, capitalism is becoming less democratic: stock ownership has become more concentrated, with the percentage of adult Americans owning stock the lowest since 1999 and a full 13 points less than 2007. The fact that poverty — reflected in such things as an expansion of food stamp use — has now spread beyond the cities to the suburbs, something much celebrated among urban-centric pundits, is further confirmation of the yeomanry’s stark decline.

How our political leaders respond to this challenge of downward mobility will define the future of our Republic. Some see a future shaped by automation that would “permanently end” what one author calls “the age of mass human labor,” allowing productivity to rise without significant increases in wages. In this world, the current American middle and working class would be economically passé.

One would hope business would have a better option that would restart upward mobility. Lower taxes on the investor class, less regulation of Wall Street, and the mass immigration of cheap workers — all the rage among investment bankers, tech oligarchs and those with inherited wealth — does not constitute a compelling program of middle-class uplift. Nor does resistance, particularly among the Tea Party, to make the human and physical infrastructure investment that could help restore strong economic growth.

Fortunately history gives us hope that this decline can be turned around. The early decades of the Industrial Revolution saw a similar societal decline, as once independent artisans and farmers became fodder for the factory lines. Divorce and drunkenness grew as religious attendance failed. But a pattern of reform, in Britain, America and even Germany, helped restore labor’s place in the economy, and rapid growth provided the basis not only for the expansion of the middle class, but remarkably improvements in its well-being.

A pro-growth program today could take several forms that defy the narrow logic of both left and right. We can encourage the growth of high-wage, blue-collar industries such as construction, energy and manufacturing. We can also reform taxes so that the burdens fall less on employers and employees, as opposed to those who simply profit from asset inflation. And rather than impose huge tuitions on students who might not finish with a degree that offers employment opportunities, let’s place new emphasis on practical skills training for both the new generation and those being left behind in this “recovery.” Most importantly, the benefits of capitalism need be more widely shared if business hopes to gain support from the middle class for their agenda.

This story originally appeared at Forbes.com.

Joel Kotkin is executive editor of NewGeography.com and Distinguished Presidential Fellow in Urban Futures at Chapman University, and a member of the editorial board of the Orange County Register. He is author of The City: A Global History and The Next Hundred Million: America in 2050. His most recent study, The Rise of Postfamilialism, has been widely discussed and distributed internationally. He lives in Los Angeles, CA.