NEW YORK – To veterans of past social movements, the Occupy Wall Street protests that began in New York and spread nationwide have been a welcome response to corporate greed and the enfeebled economy. But whether the energy of protesters can be tapped to transform the political climate remains to be seen.

“There’s a difference between an emotional outcry and a movement,” said Andrew Young, who worked alongside the Rev. Martin Luther King Jr. as a strategist during the civil rights movement and served as U.S. ambassador to the United Nations. “This is an emotional outcry. The difference is organization and articulation.”

The nearly four-week-old protest that began in a lower Manhattan park has taken on a semblance of organization, and a coherent message has largely emerged: That “the 99 percent” who struggle daily as the economy shudders, employment stagnates and medical costs rise are suffering as the 1 percent who control the vast majority of the economy’s wealth continues to prosper.

Labor unions and students joined the protest Wednesday, swelling the ranks for a day into the thousands, and lending the occupation a surge of political clout and legitimacy.

President Obama said Thursday that the protesters were “giving voice to a more broad-based frustration about how our financial system works;” some Republicans have been seeking to cast Occupy Wall Street as class warfare.

The growing cohesiveness and profile of the protest have caught the attention of public intellectuals and veterans of past social movements.

“I think if the idea of the movement is to raise the discontent that a lot of people from different walks of life and different persuasions have on the economic inequity in this country — it’s been perfect,” said the Rev. Al Sharpton, who plans to broadcast his nationally syndicated radio show from the park today and five days later lead a jobs march in Washington, D.C.

He said he felt it was necessary to be there to talk about how blacks and Latinos are also buffeted by the economic difficulties. “I think it is more a movement to show dissatisfaction. I think that is effective and useful,” he said.

History is littered with social movements that failed to emerge as political forces to create lasting change — including mass labor protests to end unemployment and to call attention to job injustices, said Immanuel Ness, a professor of political science at Brooklyn College and the editor of the “Encyclopedia of American Social Movements.”

He compared it to the tea party movement, saying both are raising concerns about general anxieties over the economic system.

“The messaging is directed at working people,” he said. “Both the tea party and Occupy Wall Street are arguing that something needs to change. The question is: What is the source of the problem?”

In the late 1990s, a global movement to reject corporate-driven globalization took to the streets, most famously in the U.S. by shutting down the 1999 meeting of the World Trade Organization in Seattle. In spite of several actions aimed at summits by world institutions, the “movement of movements,” as it soon came to be known, faded away.

Much like the Occupy Wall Street protests, one of the main criticisms was that it lacked a cohesive message.

Todd Gitlin, an author and former president of the Students for a Democratic Society in the mid-1960s, said the emerging movement was different.

The demands of the protesters were crystallizing around calls to tax the wealthy to address inequality, he said.

“‘We are the 99 percent’ is a clear message,” he said. “It is unfair and in fact disgusting that the American political economy is run for the benefit of a plutocracy. I don’t see how that can be misunderstood.”