After decades in which “hard hats” were described as enemies of the left, and four decades after construction workers in lower Manhattan attacked anti-war demonstrators on Wall Street, the AFL-CIO on Thursday called on its members to defend Occupy Wall Street from the NYPD as the city moved to arrest and evict protestors in Zuccotti Park.

Hard hats and hippies—together at last.

And when Mayor Michael Bloomberg and the NYPD backed off, the AFL-CIO rightly took some of the credit for what union leadership called “an amazing victory.”

“The AFL-CIO Stands with Occupy Wall Street,” president Rich Trumka declared as police announced plans to move in. The federation e-mailed members in the New York area on Thursday, NY1 reported, urging them to come to Zucotti Park and “stand guard” overnight to defend the encampment from the NYPD. “Support” doesn’t get more direct than that.

The unions also sponsored an online petition, and, after the mayor backed off, reported “hundreds of thousands” of signatures.

Today’s events marked the sharpest possible contrast to the day in May 1970, when students protesting the Kent State Killings gathered on Wall Street, and were attacked by two hundred construction workers carrying American flags and chanting “All, the way, USA!” and “We’re number one!” Rick Perlstein tells what happened in his book Nixonland: while police stood by, the workers beat students with lead pipes wrapped in flags, targeting those with the longest hair. A crowd of a thousand Wall Street workers cheered them on. “Thank God for the hard hats!” President Nixon declared, and invited Peter Brennan, head of the Building Trades Council of New York, to the White House.

I always wondered whether that hard hat action had been organized by the White House “dirty tricks” department—especially after a memo was leaked in which Nixon staffer Stephen Bull wrote to Chuck Colson, Nixon’s key political operative, “Obviously more of these will be occurring throughout the nation, perhaps partially as a result of your clandestine activity.” But the media declared, virtually unanimously, that the white union members were pro-war Nixon supporters.

Decades of de-industrialization followed by two years of economic collapse have brought disaster to the working class—and now a new political reality. And it’s not just in New York City—AFL-CIO unions across the country have endorsed Occupy Wall Street and joined actions in their communities.