Think about Winston's thoughts within 1984. He obviously had hope and belief in the proles; "..if there was hope, it lay in the proles." The reason for his belief in the proles is due to the power that they hold, as is evident for example in the scene where all the proles are yelling on the streets. Winston is given a brief vision of the power held by their sheer weight of numbers, and the awesome potential that the proles hold if properly co-ordinated is the key to their power.
Of course, if you were thinking of answering this question as an essay, you would still expand upon the other ideas and forms of powerplay in the text, but I assume you are specifically wondering about the power that the people hold in this case.