The protesters, who argue U.S. social and economic policies unfairly favor the rich, secured the backing Thursday of the largest and most influential branch of the Transport Workers Union of America.
Local 100 President John Samuelsen said the branch's 38,000 city transit workers and 26,000 retirees share the protesters' view that while the richest New Yorkers get tax breaks, lower-income residents are struggling financially and forced to foot the bill for what they characterize as Wall Street's excesses.
"They see the injustice in that and are highlighting the injustice by protesting, and we're supporting that effort," Samuelsen was quoted in the New York Daily News as saying.
The protesters -- marching since Sept. 17 in the financial district, especially at the opening and closing stock-exchange bells -- also got advice from a small grassroots political party for a specific demand they could call for.
They could call for a 50-cent Wall Street stock-trade surcharge, which it said would boost the U.S. economy at least $350 billion a year, Light Party founder Da Vic Raphael told United Press International Thursday night.
"The Republicans say we don't want to spend more money because it will incur more debt," Raphael said. "So where is the money? On Wall Street.
"The fact of the matter is, the people who precipitated this financial crisis are the people who continue to make a lot of money," said Raphael, whose party claims to represent "a synthesis of the Republican, Democratic, Libertarian and Green parties."
He said the financial-transaction surcharge would be "a windfall" economic stimulus that "everyone needs to get behind."
About 1,000 unionized registered nurses demonstrating outside the New York Stock Exchange in June called for the surcharge, saying the billions could "go back to our communities and go back to jobs and go back to healthcare."
"Main Street bailed out Wall Street. Now it's time for Wall Street to bail out Main Street," Raphael told UPI.
Occupy Wall Street did not immediately respond to a UPI e-mail requesting a comment.
The movement, whose Facebook page had more than 5,400 supporters when UPI checked Thursday night, was recently accused of not having specific demands or a long-term strategy, despite its growth to scores of other U.S. cities, including sit-ins planned for Los Angeles Saturday and Washington Oct. 6.
University of Michigan political science Professor Michael Heaney, who has studied social protest movements, told the Los Angeles Times the movement's demands could be as vague as simply calling for financial bailout programs to apply to individuals rather than banks.