Backing a major-party candidate for president would have been anathema to Michael Klonsky 40 summers ago, when the organization he led, Students for a Democratic Society, urged young people to spurn elections. “By ’68, our line was ‘Vote in the Streets,’” Klonsky told me last spring. “We thought we had to fight with Eugene McCarthy and those people.” In August 1968, protesters clashed with police outside the Democratic Party’s national convention in Chicago—but far from being political innocents who took to the streets to protest Vietnam War hawks’ capture of the Democratic presidential nomination, many of them never supported antiwar candidates McCarthy and Robert Kennedy. “Those of us who have been in the streets for the past five days didn’t give a flying fuck whether McCarthy would win or lose,” SDS declared in posters around Chicago, “and now that he’s lost, still don’t.” On the eve of the general election of that year—in which less than 1 percentage point would separate the popular-vote totals of Richard Nixon and Hubert Humphrey—Klonsky’s SDS bluntly proclaimed: “The elections don’t mean shit.”

Klonsky, whose disgust for mainstream politics led him to launch a new, Maoist Communist Party in the 1970s, today supports Barack Obama so enthusiastically that until recently he was blogging on the Illinois senator’s campaign website. And boycotting this November’s election, Klonsky maintains, would be a “tragic mistake.” He notes that Barack Obama isn’t Hubert Humphrey, 2008 isn’t 1968, and the strong movement he served back then is “relatively weak” now. “My own support for Obama is not a reflection of a radically changed attitude toward the Democratic Party,” Klonsky recently explained to me. “Rather, it’s a recognition that the Obama campaign has become a rallying point for young activists and offers hope for rebuilding the civil rights and antiwar coalitions that have potential to become a real critical force in society.”

Michael Klonsky is hardly the only ’68 radical supporting Obama this year. In 1968, when Mark Rudd organized the student strike that shut down Columbia University, the SDS chapter that he chaired ridiculed Kennedy and McCarthy as “McKennedy,” claimed that “neither peace candidate offers an alternative to the war policies of Lyndon Johnson,” and suggested “sabotage” as an alternative to voting. Rudd succeeded Klonsky as national SDS leader, presiding over the organization’s metamorphosis into Weatherman and performing “a liaison function” for the plot to bomb a Fort Dix soldiers’ dance that instead killed three Weathermen, including two of Rudd’s Columbia SDS colleagues. Today, Rudd renounces bombs, embraces ballots—and supports Obama. “Probably the biggest difference between Columbia SDS people in 1968 and in 2008 is forty years,” Rudd explained in an e-mail. “Most of us have lived with compromise our whole lives. As kids we were raving idealists who thought that ‘The elections don’t mean shit’ was a slogan that meant something to somebody. It didn’t.”

Then there’s Carl Davidson, who was one of SDS’s three elected national officers in 1968, when the organization first urged young people to refrain from voting. His disillusionment with traditional politics became so pronounced that, in the post-sixties hangover that followed, Davidson joined Klonsky in rejecting traditional politics for fringe Marxist movements. More recently, he helped organize the 2002 rally in which Obama first spoke out against the Iraq War and now serves as the webmaster of Progressives for Obama. “The last thing we need is a simple repeat of 1968, which saw Nixon and the new Right as an outcome, as well as the defeat of [Humphrey],” Davidson contends. “One thing I’ve learned. Social change is not made by elections, but it certainly proceeds through them, not by ignoring them or chasing the illusion of end runs around them.”

Former SDS president Tom Hayden is also in the Obama camp. Hayden organized the made-for-TV protest outside the 1968 Chicago convention. But the catharsis of throwing debris at the Chicago police, the purer-than-thou sanctimony that tolerated no distinction between Lyndon Johnson and Eugene McCarthy, and the exhilaration of “voting in the streets” instead of in election booths combined to ensure liberal defeats. Hayden’s orchestrated anarchy proved more damaging to Humphrey’s presidential aspirations than any dirty trick Nixon’s henchmen could have dreamed up. Klonsky remembers Hayden plotting to spread nails on a highway; another SDS leader recalls Hayden encouraging activists to firebomb police cars. If the Democrats couldn’t run a convention, many Americans wondered, how could they run the country? “Did the radicalism of Chicago elect Richard Nixon?” Hayden asked, clearly pained, in his 1988 memoir. “Having struggled with that question for twenty years, I find there is no ‘neat’ answer.”

Now Hayden is one of the organizers of Progressives for Obama. “The difference is that back then the Democratic Party was directly carrying out the Vietnam War, which meant there was no anti-war critic to vote for after Kennedy was assassinated and McCarthy defeated by the establishment,” he offered in an e-mail last month. “Today the Republican Party is directly carrying out the war, which obviously will make a lot of people favor changing the presidency despite the uncertainty of what the Democratic candidate will do when in office.”

Progressives for Obama resembles a Who’s Who of SDS luminaries. In addition to Hayden, Rudd, and Davidson, the group includes Bob Pardun, SDS’s education secretary during the 1966–67 school year; Paul Buhle, a radical professor who has recently attempted to revive SDS; Mickey and Dick Flacks, red-diaper babies who helped craft 1962’s Port Huron Statement, a seminal New Left document; and SDS’s third president, Todd Gitlin. Age and experience have mellowed some of the SDSers in Obama’s camp. Gitlin, for instance, has evolved into a respected Ivy League professor and milquetoast liberal. But others still glory in a past that can only damage Obama’s future. The aging New Left still practices a therapeutic politics that places a higher value on feelings of personal liberation than on restrained pursuit of political aims.

Obama has already taken political hits for his connection to Weathermen Bill Ayers and Bernardine Dohrn. In the sixties, Ayers advocated that young people kill their parents, and Dohrn praised the Charles Manson murders. Alongside their Weather Underground cohorts, the pair declared war on the United States and participated in a bombing campaign that hit the Capitol, the Pentagon, and numerous law enforcement agencies. The couple eventually reinvented themselves—first as academics, then as players in Chicago-area Democratic politics. Obama praised Ayers’s book in the Chicago Tribune, sat with him on a foundation’s board, and benefited from a fundraiser held at the couple’s home. Ayers spoke at events organized by Michelle Obama; Barack Obama spoke at events organized by Ayers.

With the public revelation of this unseemly relationship—between unrepentant terrorists and the man who now seeks to oversee America’s war on terror—and the impact it’s already had on voter attitudes, one would think that other sixties extremists might be more reserved in proclaiming their support for Obama, knowing the damage such associations can do to his candidacy. As for Obama, he’ll need to do some distancing of his own. He protested that he was only eight when Ayers, Dohrn, Rudd, and company embarked on their bombing campaign, and that’s reasonable enough. But he’ll need to go further.

Fortunately for him, the Left has a long history of cold-shouldering predecessors to perpetuate its ideology, cleanse it from past failures, and make it appear fresh. The New Left dissociated itself from the Old Left’s Russophilic dogmatism through the Port Huron Statement and other declarations of independence. Even the phrase “New Left” was adopted to divorce the Left from its history.

SDS’s history offers a template for eliminating the embarrassing past. Jack London, Upton Sinclair, and others founded the Intercollegiate Socialist Society (ISS) during the Progressive era, but by World War I the word “socialist” had fallen from favor. So, with the Left seeing labor unions as the agent of societal change, the ISS became the League for Industrial Democracy (LID). Then, by the end of the 1950s, theorists Herbert Marcuse, C. Wright Mills, and Norman O. Brown scoffed at the idea of blue-collar workers—often violently hostile to the Left’s aims—as transformative agents, and the LID’s student arm, the Student League for Industrial Democracy (SLID), rechristened itself Students for a Democratic Society. Just as SDS killed SLID as the fifties became the sixties, Weatherman killed SDS as the sixties became the seventies: SDS’s spirit of “participatory democracy” could not peacefully coexist with the vanguardism of Weatherman. And now, completing the circle, the SDS alumni of “progressives” for Obama resurrect a term that would have been more familiar to their distant forebears in the Intercollegiate Socialist Society. On the Left, everything old is eventually new again.

In 1968, the Left served as unwitting allies of Republicans, costing the Democrats the White House by rioting at their convention and withholding votes from Hubert Humphrey. In 2008, it is their vocal support that may cost Barack Obama the presidency. Obama can take a page from the early days of the New Left, which—initially, at least—refused to allow discredited radicals to discredit it. Either Obama publicly divorces himself from radical supporters whose association does more for them than it does for him, or he faces the prospect of Bill Ayers as his Willie Horton.