On the question of marijuana, former vice president Joe Biden might seem out of step with the crowd.

There are his competitors in the 2020 Democratic presidential primary, many of whom have said they want to legalize the drug. There’s the American public, two-thirds of which says that weed should be legal, according to new data from the Pew Research Center. Break that down into any racial, gender or educational group in the United States, and a majority of the group supports legalization — unlike Biden.

But the 76-year-old Democrat is in tune with at least one demographic: his peers in the silent generation, who, at 35 percent, have what may be one of the lowest percentages of support for marijuana legalization, according to the Pew data released Nov. 14.

This disparity on the topic came into full view at a town hall in Las Vegas over the weekend, when Biden drew some groans from the crowd by saying he wants to see more research on marijuana and suggesting that it may be a “gateway drug” that can lead users to harsher substances.

“The truth of the matter is, there’s not nearly been enough evidence that has been acquired as to whether or not it is a gateway drug,” Biden said. “It’s a debate, and I want a lot more before I legalize it nationally. I want to make sure we know a lot more about the science behind it.”

Answering an audience question, Biden indicated he is not opposed to the drug entirely. He supports the use of medical marijuana and would decriminalize possession of the drug, he said, adding that he wants individual states to make decisions on recreational use.

Nonetheless, the comments set Biden apart from most of the other Democratic presidential candidates and drew immediate backlash from his party’s left wing — including Rep. Alexandria Ocasio-Cortez (N.Y.), who recently endorsed Sen. Bernie Sanders (I-Vt.).

“Marijuana should be legalized, and drug consumption should be decriminalized,” Ocasio-Cortez tweeted Sunday. “These are matters of public health.”

Under federal law, marijuana is classified as a Schedule I substance, defined by the Drug Enforcement Administration as a drug “with no currently accepted medical use and a high potential for abuse.” (Other examples include LSD and heroin.) Biden has said he wants to make it a Schedule II drug so that its benefits and impacts can be studied further.

“It is not irrational to do more scientific investigation to determine, which we have not done significantly enough, whether or not there are any things that relate to whether it’s a gateway drug or not,” Biden said at the Las Vegas town hall.

Research to date on marijuana has pointed to a mixed record on the risks from the substance. Last week, for example, the group Smart Approaches to Marijuana pointed to the results of a study in JAMA Psychiatry showing that states that have legalized the recreational use of cannabis saw a half-percentage-point increase in rates of problematic use of the drug.

Recreational marijuana is legal in 11 states plus the District, while just four states prohibit its use in all forms.

Biden’s plan, unveiled in July, looks to cut down on high rates of incarceration and fix “the racial, gender, and income-based disparities in the system,” including by decriminalizing marijuana and expunging past convictions for possession.

Compared with Biden’s competitors in the Democratic field, that plan stops short of the kind of sweeping changes proposed by the likes of Sanders and Elizabeth Warren (Mass.). Along with nine other candidates still in the race — a plurality — they have voiced their support for legalizing marijuana on the federal level.

Throughout most of his legislative career, Biden championed tough criminal penalties for possession, including in the 1994 crime bill, which many critics have since linked to a rapid rise in mass incarceration and mass policing. Biden, who oversaw the Senate Judiciary Committee at the time, was one of the bill’s key authors, so much so that he later took to calling it the “1994 Biden Crime Bill.”

Even as he’s shifted his stance on harsh penalties for nonviolent drug crimes, Biden has a long record of skepticism toward full marijuana legalization.

Stating in 2010 his belief that it would be a “mistake to legalize,” according to Forbes, he said, “I still believe it’s a gateway drug."