Occupy Wall Street reached critical mass this week.

What began as an encampment of a few hundred protesters swelled, at least temporarily, to a mass movement as thousands of protesters jammed the financial district on Wednesday as labor and community organizations turned out their members in support of the ongoing social justice protest.

The demonstrations have also jumped onto the national political agenda. President Obama was asked twice about the protests at a news conference on Thursday. “I think it expresses the frustrations that the American people feel,” he said. “People are frustrated and the protesters are giving voice to a more broad-based frustration about how our financial system works.”

Aside from the irony of Obama expressing sympathy with a movement that is at least partly an indictment of his administration, what is interesting about Obama’s statement is that it is a concise summary of the spirit of the protests. One of the central criticisms of the Wall Street protests has been the lack of a clear demand, and yet even the president gets the underlying grievance driving people into the streets.

If the signs brandished by individual protesters on Wednesday were any indication, the demands are a wide variations on the theme of accountability in the financial system. They ranged from the conventional (“Hands off my Social Security!”) to the radical (“Take your money back: Nationalize the banks under worker control”) to the humorous (“You know it’s bad when librarians are marching!”).

This ideological diversity could be seen as a demonstration of the advantages of not having a clear platform: the protest is many things to many people, which means more protesters show up.

Police challenge

As the demonstrators ranks swelled, so did those of the police. On Wednesday NYPD helicopters hovered overhead while on the ground hundreds of uniformed police officers corralled the marchers into lanes designated for the protest, lined by metal barricades and the infamous orange nets seen at previous protests.

The barricades were a source of friction. At one point Wednesday I stood in a crowd of hundreds of demonstrators waiting for 20 minutes just to turn the corner where police had created a bottleneck with the barricades. “Let us march!” the crowd chanted. A young man suggested that the crowd move the barricade themselves. The police didn’t budge, and the protesters hesitated to begin an open confrontation. “They just want to show us who is in control,” one man remarked to me.

Later on Wednesday, two dozen people were reportedly arrested night after protesters attempted to march to Wall Street proper, and one police officer was videotaped using a baton to beat back a number of demonstrators.

Arrests and police violence have provided much of the drama in the three-week old saga of Occupy Wall Street. Deputy Inspector Anthony Bologna’s pepper-spray attack, and the mass arrests on the Brooklyn Bridge last weekend, when protesters did openly confront the police, brought more attention to their actions, and perhaps encouraged more people to join them this week.

Many now speculate that the endgame of the protest could be a police eviction of the protesters camped out in Zuccoti Park (Liberty Plaza). The police say it’s up to Brookfield Properties, the real estate company that owns the private park, whether to declare the occupiers trespassers. Justin Elliot of Salon reported Thursday that Mayor Michael Bloomberg’s girlfriend, Diana Taylor, sits on the board of that company.