Hers is a movement without a clear leader, one in which crowds of largely young people are organizing themselves and acting on their own, overtaking months of planning by veterans of the city’s pro-democracy camp. The spontaneous, grass-roots nature of the protest is one of its strengths — it has adapted quickly and seized the momentum from the government — but it may also make it difficult for the movement to accept any compromise that the Chinese government might be willing to offer.

The mass sit-in — and for hardier participants, sleep-in — in several of Hong Kong’s key commercial districts has presented the Chinese leadership with one of its biggest and most unexpected challenges in years. The protesters are demanding the right to elect the city’s leader, or chief executive, without procedural hurdles that would ensure that only Beijing’s favored candidates get on the ballot.

China’s state-run news outlets have depicted the protests as the handiwork of a conspiracy aided by the West to topple the Communist Party. But what leaders in Beijing and Hong Kong face is something even more alien to party thinking: an amorphous movement that does not answer to any particular individual or agenda.

The protesters’ desire for democratic elections was first articulated by organizations dominated by academics and students, but the movement that has blockaded the city streets since the weekend is a cacophony of voices, with demands including face-to-face dialogue with the Chinese government’s handpicked chief executive, Leung Chun-ying; his immediate resignation; and more ambitious, and unlikely, concessions from the central government.