Once upon a time, socialists running for president in the United States had to explain that while they had no chance of actually winning an election, their campaigns were aimed at “educating” voters — about socialism.

As a successful politician twice elected to the U.S. Senate and showing very respectable numbers in most presidential primary polls, Bernie Sanders needs no such excuse. He assures voters that he is running to win and there is no reason to doubt him. But win or lose, his campaign nevertheless is proving highly educational for Americans perpetually perplexed by the meaning of “socialism.” Or as Sanders sometimes specifies, “democratic socialism,” or the even milder “social democracy.”

Since the advent of the Cold War and even before then, the multifarious meanings of the S-word were hidden behind the ideological and cultural defenses erected against communism. The Soviet dictatorship and its satellites claimed their authoritarian way was the only true socialism – and conservatives in the West seized that self-serving claim to crush arguments for social justice and progressive governance. American politicians of both parties embraced the blurring of socialism with communism.

But that narrow definition of socialism was always wrong. To accept it meant to ignore fundamental realities, both contemporary and historical – such as the bolstering of the Western alliance by European democracies that called themselves “socialist” or social democratic, all of which had adopted programs, such as universal health care, denounced by American politicians as steps on the road to Communist serfdom. Decades later, of course, those same countries – including all of Scandinavia, France, Germany, the United Kingdom – remain democratic, free, and open to enterprise.

As for the United States, Sanders might recall that this country once had a thriving Socialist Party, which elected mayors in cities like Milwaukee and even sent two of its leaders, Milwaukee’s Victor Berger and New York’s Meyer London, to Congress. Their movement enjoyed not only electoral victories but a strong record of municipal reform and reconstruction. They built sewers to clean up industry’s legacy of pollution; they built public housing; they ensured delivery of publicly owned, affordable water and power; and they cleaned up local government.

Between the triumph of the New Deal and the devastation of McCarthyism, the political space for American socialism virtually vanished. Before they were relegated to the margins, however, the socialists strongly influenced the direction of American social policy.

Long after the various socialist parties had faded, their heirs continued to serve as the nation’s most insistent advocates for reform and justice. Socialists (and yes, communists), were among the leading figures in the civil rights, labor, and women’s movements. It was a remarkable 1962 book by the late, great democratic socialist Michael Harrington, The Other America, that inspired President Kennedy and his brothers to draw attention to the continuing shame of poverty in the world’s richest nation. When Ronald Reagan warned in 1965 that Medicare was a hallmark of “socialism,” he wasn’t too far from the mark – except that 50 years later, the popular program has liberated older Americans, not enslaved them.

Now Bernie Sanders has taken up the old banner in a political atmosphere where more voters – and especially younger voters — are receptive to calm debate instead of hysterical redbaiting.

Certainly Hillary Clinton, whatever her view of Sanders’ ideology, understands social democracy: When her husband was president, the democratically elected socialist leaders of Western Europe were his closest international allies. In her first book, It Takes A Village, she highlighted many of the same social benefits in France, Germany, and the Scandinavian countries that Sanders advocates today.

So Clinton knows very well that “socialism,” as her primary rival uses that term, is no frighteningly alien worldview, but merely another set of ideas for organizing society to protect and uplift every human being.

It is long past time for the rest of the American electorate to learn that, too.

Democratic presidential candidate Sen. Bernie Sanders (I-VT) takes part in a rally to preserve union pensions on Capitol Hill in Washington September 10, 2015. REUTERS/Joshua Roberts