An audacious escape by blind dissident Chen Guangcheng is the second uproar this year to hit Zhou, who has expanded China's policing apparatus into a vast, costly and - now for all the world to see - a flawed tool of Communist Party control. But even one of the biggest domestic security embarrassments in more than a decade is unlikely to knock him out before a party congress late this year that will appoint successors to him and other retiring leaders, said several experts.