The bill, which reflects growing support for legalization, would end the federal prohibition on cannabis. But it is unlikely to pass in an election year and a divided government.Senate Democrats reintroduced broad legislation on Wednesday to legalize cannabis on the federal level, a major policy shift with wide public support, but it is unlikely to be enacted this year ahead of November’s elections and in a divided government.The bill, which amounts to a Democratic wish list for federal cannabis policy, would end the federal prohibition on marijuana by removing it from a controlled substances list. The government currently classifies the drug as among the most dangerous and addictive substances.The legislation would create a new framework regulating cannabis and taxing the burgeoning cannabis industry, expunge certain federal marijuana-related offenses from criminal records, expand research into marijuana’s health impacts and devote federal money to helping communities and individuals affected by the war on drugs.The measure, which was first introduced in 2022, was led by Senators Chuck Schumer of New York, the majority leader; Ron Wyden of Oregon, the chairman of the Finance Committee, and Cory Booker of New Jersey. Fifteen other Senate Democrats have signed on as co-sponsors.“Over the decades, millions of Americans, most often Americans of color, have had their lives derailed and destroyed by our country’s failed war on drugs,” Mr. Schumer, the first majority leader to call for federal legalization, said on the Senate floor on Wednesday. “In place of the war on drugs, our bill would lay the foundation for something very different: a just and responsible and common-sense approach to cannabis regulation.”He reintroduced the measure one day after the Justice Department recommended easing restrictions on cannabis and downgrading it to a lower classification on the controlled substances list. That move did not go as far as some advocates and many Democrats have urged, but it was a significant shift reflecting the Biden administration’s efforts to liberalize marijuana policy.“Reclassifying cannabis is a necessary and long-overdue step, but it is not at all the end of the story,” Mr. Schumer said. “It’s time for Congress to wake up to the times and do its part by passing the cannabis reform that most Americans have long called for. It’s past time for Congress to catch up with public opinion and to catch up with the science.”But despite support from top Democrats, the legislation is highly unlikely to move in Congress during this election year. Republicans, many of whom have opposed federal cannabis legalization, control the House, and none have signed on to the bill. Congress has also labored to perform even the most basic duties of governance amid deep divisions within the Republican majority in the House. And few must-pass bills remain, leaving proponents without many opportunities to slip it into a bigger legislative package.Kevin Sabet, who served as a drug policy adviser during the Obama, Bush and Clinton administrations, warned about the dangers of legalization and argued that such a bill would “commercialize” the marijuana industry and create “Big Tobacco 2.0.”“Let’s not commercialize marijuana in the name of social justice,” said Mr. Sabet, now the president of Smart Approaches to Marijuana, an anti-legalization advocacy group. While he supported certain elements of the bill, such as expunging criminal records and removing criminal penalties for marijuana use, he said legalization was ultimately about “supersizing a commercial industry.”“And we really have to think long and hard after our horrible experience with Big Tobacco in our country,” he said, “whether that’s going to be good for us or not.”Still, the legislation reflects growing support among Democrats and across the country in both Republican- and Democratic-leaning states for legalizing access to marijuana, in addition to the issue’s potential political value ahead of an expected election rematch between President Biden and former President Donald J. Trump.Legalization, in some form, is broadly popular across the country, with 88 percent of Americans saying marijuana should be legal for medical or recreational use, according to a January survey by the Pew Research Center. Twenty-four states have legalized small amounts of marijuana for adult recreational use, and 38 states have approved it for medicinal purposes. And where marijuana legalization has appeared on state ballots, it has won easily, often outperforming candidates in either party.Advocates of legalization have emphasized the issue’s political potency in trying to convince elected officials.“If anybody was looking at the political tea leaves, they would have to realize that obstructing cannabis policy reform — it is a losing proposition as a politician,” said Morgan Fox, the political director of the National Organization for the Reform of Marijuana Laws, an advocacy group. “This is really a rallying point for people that care about cannabis policy reform.”At least one Democrat, Representative Earl Blumenauer of Oregon, a leading cannabis advocate in Congress, has urged the Biden administration to embrace full legalization and make it a more prominent part of Mr. Biden’s re-election campaign. He has argued that the issue could help the president engage young people, whose support for him has faltered, but who could be crucial to victory in November.The Biden administration’s move to downgrade cannabis on the controlled substances list also reflects the president’s evolution on the issue. Mr. Biden has pardoned thousands of people convicted of nonviolent drug offenses in an effort to remedy racial disparities in the justice system. And Karine Jean-Pierre, the White House press secretary, has emphasized that Mr. Biden had been “very, very clear he doesn’t believe that anyone should be in jail or be prosecuted just for using or possessing marijuana.”Mr. Trump’s record on legalization is more mixed. In 2018, his administration freed prosecutors to aggressively enforce federal marijuana restrictions in states that had eased prohibitions on the drug. Mr. Trump later appeared to break with his administration, saying he was likely to support a legislative proposal to leave legalization to states, and he pardoned several nonviolent drug offenders.“This has not been an issue that is really coming up in conversation, at rallies or in media appearances and whatnot,” Mr. Fox said. “It’s kind of an unknown, how a future Trump administration would deal with cannabis.”Congress is considering more incremental bills that would ease restrictions on marijuana — such as by allowing legal cannabis businesses to access financial services — several of which have bipartisan support. But most are not expected to move during this Congress, given Republican opposition. More