Shortly after formally announcing his entrance into the presidential race Thursday, Sen. Bernie Sanders appeared at a brief press conference in Washington, D.C., during which he described himself as “a guy, indisputably, who has the most unusual political history of anybody in the United States Congress.”

That's no exaggeration: Sanders has the distinction of being the longest-serving independent member of Congress in its history.

Though Sanders will be challenging presumptive front-runner Hillary Clinton for the Democratic nomination, and though he caucuses with the Democrats in the Senate, the Vermont senator has never officially served as a member of the party. And unlike any of his colleagues in the legislative branch, when asked to describe his views, he calls himself a democratic socialist.

Self-identified socialists have run for president before, but virtually all the socialist candidates of the past century have languished in obscurity. Sanders may be the most prominent socialist to seek the presidency since labor leader Eugene Debs ran on the Socialist Party ticket in 1912. Sanders is also the only professed socialist ever to seek the Democratic nomination for president.

The odds that Sanders will defeat Clinton are slim. Yet the very fact of his candidacy is a big step forward for a political ideology that has sat on the electoral margins since the end of the Cold War, according to John Nichols, Washington correspondent for The Nation and author of a book on the history of American socialism, “The S Word.”

“In the last 25 years, democratic socialism has been pushed so far to the edge of the discourse,” he said. “And so I think Sanders running brings it a little back to perhaps where it was 25 years ago."

There are other indicators that American socialism might be undergoing something of a revival. Socialist-leaning publications such as Jacobin and Dissent have attracted some favorable coverage from mainstream outlets like the New York Times. And in 2013, Kshama Sawant became the first socialist in at least a century to be elected to citywide office in Seattle.

Public attitudes to socialism have softened in recent years, facilitating the minor comeback. A 2011 Pew survey found that young people between the ages of 18 and 29 felt slightly more favorably toward socialism than toward capitalism. A 2014 Reason-Rupe poll found that 36 percent of respondents viewed socialism favorably, including 52 percent of Democrats.

Members of the Democratic Party’s left flank have plenty of common ground with democratic socialists in the Bernie Sanders mold, according to Michael Kazin, a Georgetown University historian, Dissent co-editor and Bernie Sanders supporter.

“Most of his stances are those of Elizabeth Warren, who is not a socialist as far as I know,” said Kazin. “There’s a tradition of socialists saying a lot of the same things that Elizabeth Warren has been saying, that even Obama has said to a certain extent."

The particular brand of socialism espoused by Bernie Sanders, called democratic socialism, is a far cry from the authoritarian Soviet model, said Kazin. It has far more in common with the politics of social democratic parties found across Western Europe.

“He’s the kind of socialist who in Europe would be in the British Labour Party, would be in the French Socialist Party," Kazin said. "His positions would be on the left wing of some of those parties, but he would be a member of one of the parties which is now often a governing party.”

In describing his own politics, Sanders has often used the social democratic Nordic model as his touchstone.

“We have a lot to learn from democratic socialist governments that have existed in countries like Denmark, Sweden, Finland, [and] Norway,” he told Fox News host Bill O’Reilly during an appearance on the network last year. “Where all people have health care as a right, where higher education is free, where they have a strong child care program, where they don’t have the massive type of wealth and income inequality that we have in the United States of America."

Nichols said that he hopes Sanders will be able to “articulate a new vision of politics” in his campaign and perhaps widen the range of acceptable political viewpoints in mainstream American politics.

“What are they going to do?” Nichols said of Sanders’ opponents on the right. “Call him a socialist?"