Marijuana legalization features prominently in 2020 Democrats' criminal justice reform plans, but many repeat the common misbelief that the drug plays a major role in mass incarceration.

Criminal justice reform is a hot issue in the 2020 Democratic primary, with candidates competing to release the most progressive platform. Their focus on marijuana legalization to help tamp down on mass incarceration is based on a myth, as the drug plays almost no role in mass incarceration, according to federal data. Democrats' emphasis on it avoids hard questions about violent offenders, according to some criminal justice experts.

Every major 2020 candidate has called for federal legalization of marijuana, with the exception of former vice president Joe Biden, who supports decriminalization but leaves legalization to the states. Many candidates have also backed expunging marijuana offenders' records and pardoning all federal marijuana possession offenders.

There are lots of reasons Democrats have come out so strongly in support of marijuana—for one, 66 percent of Americans, including 75 percent of Democrats, support legalization. But front and center in almost all arguments for marijuana legalization is the same claim: Its criminalization is a major driver of America's large prison population.

Sen. Kamala Harris's (D., Calif.) criminal justice plan, for example, cites the prison and probation population charged with drug offenses to conclude that "it is past time to end the failed war on drugs, and it begins with legalizing marijuana" (emphasis in the original). In a list of "five ideas for reforming our criminal justice system," former Rep. Beto O'Rourke's (D., Tex.) number one proposal to lower America's incarceration rate is to end federal marijuana prohibition and expunge offenders' records. In her plan, Sen. Elizabeth Warren (D., Mass.)—a former marijuana skeptic—calls the "war on drugs" a destructive failure, and promises to end it through legalization.

Although these are the most aggressive examples of the marijuana-incarceration link, weed appears in basically every major candidate's criminal justice platforms, including Mayor Pete Buttigieg (D., Ind.), Sen. Bernie Sanders (I., Vt.), Biden, and Andrew Yang.

The 2020 Dems are not the only ones to see marijuana prohibition as a major driver of incarceration. Rep. Alexandria Ocasio-Cortez (D., N.Y.) invoked it after drawing flack for appearing to endorse prison abolition. Ocasio-Cortez backtracked on that proposal, but argued that "many people in jailed [sic] or in prison don’t belong there at all," offering "punitive sentencing for marijuana possession" as her leading reason why.

The marijuana-incarceration link is popular among the organizing left, too: A 2020 Netroots Nation panel, for example, calls marijuana arrests "the gateway to mass incarceration." The idea has become common wisdom across the political spectrum. In a 2016 poll, majorities of liberals, conservatives, and independents said they believed that "nearly half of all U.S. prisoners are incarcerated for drug offenses."

Democrats are right that America incarcerates a lot of people—roughly 2.3 million, which makes for the highest official per capita rate in the world by some estimates. Polls find that most Americans want to reduce that number. Given strong popular support for both marijuana and reducing the prison population, Democrats could hit a political home run by achieving both goals through legalization.

There's just one problem: The data indicate that drug possession in general, and marijuana possession or trafficking in particular, have essentially no impact on mass incarceration.

"The direct impact of marijuana legalization on state prison populations would be slim to none," Professor John Pfaff of Fordham told the Washington Free Beacon. "Its impact on county jail populations, which hold pre-trial detainees and those convicted of lower-level, misdemeanor offenses, would likely be bigger—but thanks to shoddy jail data, we don't know by how much."

Pfaff is a vocal critic of the marijuana-incarceration argument. He identifies as an advocate of criminal justice reform, but has worked hard to debunk myths, such as the marijuana-incarceration connection, that he believes constrain reform and mislead the public.

Prisons in the United States are administered by two separate entities: the federal government and the states. The most recent figures show that states incarcerate about 1.3 million people, while the feds incarcerate roughly 160,000.

About half of federal offenders are incarcerated for drug-related offenses. But those offenders are A) 99-percent trafficking offenders, and B) overwhelmingly unlikely to have committed a drug offense involving marijuana. Of the 20,000 drug offenders admitted to federal prison in 2017, only 2,800 were marijuana offenders, and a scant 92—0.4 percent of the total—were in for possession. Federal marijuana offenders also receive the shortest average sentence of any drug offender.

Pinning down marijuana offenders at the state level is harder to do, because not every state reports data. In general, drug offenders make up 14.8 percent of state-level incarcerees, with just 3.5 percent of those being possession offenders. Pfaff told the Free Beacon that in his review of incomplete state-level data, he concluded that "something on the order of 1 percent of all [people] in prison" are there for marijuana.

In other words: Legalizing marijuana tomorrow would have minimal impact on mass incarceration. In fact, legalizing all drugs tomorrow, a proposal few Americans support, would have a minimal impact.

"Freeing every single person who is in a state prison on a drug charge would only cut state prison populations back to where they were in 1996-1997, well into the ‘mass incarceration' period," Pfaff writes in his book, Locked In.

Why Democrats continue to press the marijuana-incarceration link, despite its status as myth, is unclear. The data point to one possible explanation. At the state level, 55 percent of individuals incarcerated are in on violent charges, including rape and murder; another 17.5 percent face property crime charges, such as burglary. Putting a true dent in the incarcerated population would mean releasing violent offenders back on to the streets.

That release would not be nearly as politically popular as weed legalization. The same poll that found Americans believe most incarcerated individuals are drug offenders also found that 60 percent oppose releasing "people who committed a violent crime and have a low risk of committing another crime." That includes majorities of self-identified liberals, moderates, and conservatives.

Progressive criminal justice reform groups such as the Sentencing Project and Cut50 have pushed to expand decarceration efforts to violent offenders. But at least for now, even the most progressive 2020 Democrats do not seem to be biting.