(Rich Pedroncelli/AP)

During the most recent Republican presidential debate, the candidates called mass incarceration a major problem. With 2.2 million Americans now incarcerated — triple the number locked up in the 1980s when President Ronald Reagan escalated a “war on drugs” and legislators vied with one another to appear toughest — the United States holds the dubious distinction of being the world’s largest jailer. Black Americans are nearly six times as likely as whites to end up in prison or jail, and Latinos are more than twice as likely.

Getting “tough on crime” after the 1960s

As many know, poor black and Hispanic men who live in isolated urban districts are the ones disproportionately incarcerated and watched by police. In the decades following 1960s civil rights victories, fears of racial integration coincided with a sharp rise in violent crime — which soared from 160 per 100,000 people in 1960 to more than 750 in the early 1990s before falling steadily to 375 in 2014.

Policymakers exploited white fears of black criminality by passing harsh criminal penalties. For example, in the 1980s and 1990s, lawmakers passed three-strikes laws requiring sentences of 25 years to life for a third offense, including a drug violation or petty theft that may not have resulted in a prison sentence in previous decades. Policymakers also embraced mandatory 10-, 20-, and 30-year minimum sentences for violent and nonviolent acts, and increased the number of offenses resulting in life sentence without parole.

Being “tough on crime” was considered the way to win reelection from anxious white voters, and from some black voters living in communities subject to the most violence and the least police protection.

Mass incarceration is expensive and offensive

Since then, mass incarceration has proven to be unsustainably costly. At the same time, moral opposition is growing to a system that is seen as racially biased and overly punitive for drug-related and nonviolent crimes.

Interest groups on the left and the right are finding common cause in prison reform, with backing both from the American Civil Liberties Union, Americans for Tax Reform, the tea party-affiliated Freedom Works and arch-conservative Koch Industries. Locally and nationally, Republicans and Democrats together are crafting proposed reforms to moderate mandatory sentencing and drug laws. Both Republican and Democratic presidential hopefuls are denouncing harsh punishments for nonviolent offenders. Some states are experimenting with the decriminalization of marijuana. Many observers are optimistic that mass incarceration will soon be undone.

But reform may not be as easy as these signals suggest.

The roadblocks to reform: new jobs and more populous districts

In fact, there are more deep-seated — but less visible — obstacles to dismantling the prison apparatus.

First, there is a common misperception perpetuated by mainstream politicians who want to reform the criminal justice system that most prisoners are nonviolent drug offenders. This idea is false.

The second reason is more disturbing. Mass incarceration solved two major problems for a country whose collapsing industrial base left the poor and working classes without jobs.

The “tough on crime” movement did this in two ways. First, outsize numbers of jobless young black men who lived in impoverished urban districts were designated as criminals, taken off the streets and put in warehouses. Second, prisons became a jobs program for rural America.

Previously, in the 1960s — when U.S. incarceration rates were relatively stable and on par with other Western democracies — most prisons were located in the metropolitan areas where prisoners were typically arrested and where they had last had an address. But expanding prisons there would have been expensive and controversial, with both land and labor in shorter supply.

Instead, rural communities built hundreds of prisons in the 1980s and 1990s, accounting for most new prison growth. Local policymakers took advantage of the expanding prison sector’s demand for cheap land and untapped labor to bring jobs and capital to economically distressed, rural communities.

The self-perpetuating politics of rural prisons

The political consequences are self-perpetuating. Alhough prisons do not typically improve the local economy in the long run, many underdeveloped rural spaces don’t have other jobs available. They come to rely on prisons for jobs and revenue, as much as if it were a new textile or auto parts factory. That creates political pressure to keep prisons full.

Second, the federal census counts prison inmates as residents of the communities where the prison is located. That inflates population counts in otherwise shrinking rural areas — and determines both how many political representatives the area gets as well as the formulas for state and federal support for such services as social welfare and economic development.

As a result, prison towns get more political representation and more local funding. Meanwhile, predominantly non-white urban communities lose both.

Do legislators with prisons in their districts fight sentencing reform?

For a recently published article, I compiled the location, size and operating capacity of state, federal and private prisons in California, New York and Washington state from 2000 to 2010. With this, I examined whether state legislators who represented rural communities with prisons were more likely to support harsh criminal punishments for nonviolent offenses than their fellow legislators in the same party and with similar politics.

The answer, in a word: Yes.

State lawmakers representing rural communities with correctional institutions make up a consistent and powerful voting bloc to uphold harsh sentencing laws and block criminal law reform. Prison jobs are extremely important for rural communities. That’s why some Democratic state legislators routinely defy their party’s leaders and oppose measures to curb imprisonment. Their districts’ reliance on prison jobs and capital trumps any concerns about state budgets and partisan pressures.

Rural communities that host prisons support punitive criminal laws and policies and lobby against reform not simply because of concerns for public safety, but also because they profit politically and economically from prison growth.

Rebecca U. Thorpe is assistant professor of political science at the University of Washington and author of “Perverse Politics: The Persistent of Mass Incarceration in the 21st Century” (Perspectives on Politics, September 2015) and “The American Warfare State: The Domestic Politics of Military Spending”(Chicago 2014).