Behind Mayor Zohran Mamdani's stunning electoral victory was a grass roots volunteer operation that saw 100,000 volunteers knock on three million doors and make 4.5 million calls to engage voters. Mr. Mamdani announced on Friday that he wants to bring that level of public participation to City Hall. Sitting in Grand Army Plaza in Brooklyn, he signed an executive order creating an Office of Mass Engagement to help New Yorkers participate in government decisions and to reach communities that have been marginalized from the process.