During the 1930s, conservatives repeatedly alleged that Franklin Roosevelt was really a socialist. Today, Bernie Sanders said they were right.

In a long-awaited speech heralded as providing his definition of “democratic socialism,” the Vermont senator and Democratic presidential candidate on Thursday afternoon told a packed crowd of Georgetown University students—most of whom waited hours in a drenching rain to hear him—that by democratic socialism, he meant the economic and social principles laid down by FDR, most particularly in his 1944 State of the Union Address. In that speech, Roosevelt proclaimed that the nation needed a second, economic bill of rights. Sanders quoted the passage in which Roosevelt laid out the philosophic basis for such an expansion of rights: “True individual freedom,” Roosevelt said, “cannot exist without economic security and independence. Necessitous men are not free men.” The Vermont senator ran down the list of rights that Roosevelt enumerated: a decent job at decent pay, time off from work, a decent home, health care, and, for businesses, “an atmosphere free from unfair competition and domination by monopolies.”

The only other figure Sanders cited as shaping his vision of socialism was Martin Luther King Jr. (Unlike FDR, King did indeed identify himself a democratic socialist, as did such other key civil-rights leaders as A. Philip Randolph, Bayard Rustin, and James Farmer. Roosevelt called himself various things—most commonly a liberal, and once, when asked his philosophy, responded that he was “a Christian and a Democrat”—but never a socialist.) King, said Sanders, followed in FDR’s footsteps in proclaiming the need for economic as well as civil rights.

Getting down to particulars, Sanders continued that democratic socialism meant creating an economy that works for all, a universal health-care system based on the principle that health care is a right, free tuition at public colleges and universities (and higher Pell Grants and lower interest rates on student loans, which would also make private colleges more affordable), a governmental commitment to full employment, a living wage (with a minimum wage of $15), paid family and medical leave, more progressive taxation, and the automatic voter registration of all Americans when they turn 18.

As the socialist and social democratic parties throughout the West have been doing for 70 years, Sanders disavowed what was perhaps the classic definition of democratic socialism before World War II. “I don’t believe the government should own the corner drug store or the means of production,” he said, “but I do believe that the middle class and the working families who produce the wealth of America deserve a fair deal.”

When Roosevelt was president, of course, socialists did believe that the government should own many major industries. The Socialist Party leader in Roosevelt’s time was Norman Thomas, who won almost a million votes in the 1932 election in which Roosevelt ousted Herbert Hoover. By establishing Social Security, granting workers the right to form unions and bargain collectively, and employing millions of the unemployed on the projects (chiefly but not exclusively construction) of the federally funded and operated Works Progress Administration, however, FDR co-opted a share of the socialists’ program, causing such longtime pillars of Socialist Party support as the garment and clothing workers unions to switch their allegiance to Roosevelt and the Democratic Party. So did most of those who had voted for Thomas in 1932. Writer Upton Sinclair, a longtime socialist activist, followed this course to its logical conclusion: He ran and won in the 1934 Democratic primary for governor of California, though a red-baiting campaign by the Republicans ensured that he lost the general election that November.

Beginning in the late 1950s, a number of American democratic socialists began to argue that they should go into the Democratic Party without abandoning their ideology. (The total number of American democratic socialists in the late 1950s, I should add, was almost surely smaller than the crowd that gathered today in the Georgetown auditorium to hear Sanders.) That argument received its fullest expression from Michael Harrington, Thomas’s successor as the leader of socialist movement, who argued in his 1967 book Toward A Democratic Left, that the presumably socialist-free American political landscape actually harbored within the Democratic Party what he termed “a hidden social democracy.” The nation’s more progressive unions, the civil-rights activists, the middle-class liberals (then mounting protests against the Vietnam War)—these were the groups whose European counterparts made up those nations’ social democratic parties. Accordingly, Harrington concluded, American socialists should enter—publicly, unashamedly—the Democratic Party, those hidden social democrats’ political home, where they could work for the kinds of social changes attainable in everyday politics while also campaigning for a future of a more democratic economy and society. In 1973, he founded an organization, the Democratic Socialist Organizing Committee (now known as the Democratic Socialists of America), which did just that. (Full disclosure: I’m a vice-chair of DSA, though—also full disclosure—I haven’t been to a DSA meeting in years.)

While in college in the late 1950s and early 190s, Sanders belonged to a DSA precursor, the Young People’s Socialist League, whose chief activity was supporting the civil-rights movement. Since then, he has not been a member of any socialist organization. While DSA urged socialists to work within the Democratic Party, without forfeiting their right to criticize the party’s numerous shortcomings, Sanders steered clear of the Democrats as well. In matters of political affiliation, Bernie isn’t much of a joiner. Once he got to Congress, however, and then the Senate, he did join and take an active role in those bodies’ Democratic caucuses.

In a certain sense, what Sanders accomplished today was to signal that the political space between America progressivism and social democracy—at least, as he defines them—has shrunk to insignificance. Clearly, this has not always been the case; it’s taken the dysfunctions of American capitalism that have accumulated over the past 40 years to push progressives, and with them, the center of the Democratic Party, to the left, to within spitting distance of those who call themselves social democrats, or, in Sanders’s case, democratic socialists. By anointing Roosevelt to be the father of them all—liberals and socialists both—Sanders has proclaimed an end to such distinctions. To be sure, calling for Medicare for All places him more on the social-democratic side of the ledger, but then, it places Lyndon Johnson there as well.

If Sanders’s surprising success (thus far) in running as a socialist is partly a function of the widespread recognition of those capitalist dysfunctions, it’s also in part the result of the collapse of the Soviet Union. The great American socialist leaders of the 20th century—Eugene Debs, Thomas, and Harrington—had to make continually clear that their brand of democratic socialism had nothing in common with Soviet communism and its totalitarian progeny, which they each articulately condemned. Sanders labors under no such handicap: The anti-socialist and anti-liberal leaders who deliberately conflated Rooseveltian liberalism with Stalinist communism (the young Richard Nixon was a master at this) were put out of work with the fall of the Berlin Wall.

As the New Deal programs and policies took root on American soil, some observers occasionally remarked that the Roosevelt Democrats had carried out the Thomas socialist platform. Noting the shortcomings of New Deal liberalism (its alliance with the segregationist South and its failure to enact universal health care, among other things), Thomas responded by grumbling, “They carried it out on a stretcher.” Sanders might not contest that judgment, but in harking back to FDR’s 1944 Economic Bill of Rights, he has reconciled the most visionary statement of Rooseveltian liberalism’s aspirations with the democratic socialist tradition—or, more precisely, claimed it as the foundation of his own socialist beliefs.

A recent CBS/New York Times poll found that 56 percent of Democratic voters hold a favorable view of socialism—a figure that exceeds Sanders’s own level of support in that poll by 25 percentage points, which means that a goodly chunk of Hillary Clinton’s backers hold that view as well. What all those Democrats mean by socialism is anybody’s guess, but I suspect their sense of it is close to Sanders’s: An anti-plutocratic and egalitarian commitment to re-democratize the nation; a belief in economic rights; and a sense that the boundaries between socialism and liberalism are at minimum very porous. The cognoscenti might see themselves as the children of Thomas and Harrington, but most would see themselves as the children of Roosevelt and King. Sanders’s message to them all is: They’re right.

Harold Meyerson is the executive editor of The American Prospect and a columnist for The Washington Post. His email is hmeyerson@prospect.org. Follow @HaroldMeyerson