New York City Council

On January 7, 2010 Greenfield announced his candidacy on the Zev Brenner radio show to replace Simcha Felder.^[10] Felder announced his resignation after accepting the post as the new deputy comptroller for accounting and budget under John Liu.^[11] Greenfield received endorsements from U.S. Senator Joseph Lieberman, then-Mayor Michael R. Bloomberg, former Mayor Ed Koch, and State Senators Carl Kruger, Martin J. Golden.^[12] He received the support of council members Domenic Recchia, Lewis Fidler, Michael C. Nelson, and Vincent J. Gentile, as well as the backing of the Kings County Conservative Party, Democratic county leader Vito Lopez, and Citizens Union.^{[13][14][15][16]}

He was elected in his first term by his Brooklyn colleagues to co-chair the Brooklyn delegation and serve as their representative on the Budget Negotiating Team of the New York City Council.^[17] He later became the chair of the Land Use Committee of the New York City Council.^[18]

Greenfield has appeared as a commentator on many national news shows including Fox & Friends ^[19] and is a frequent political commentator in The New York Times and The Wall Street Journal.^[20]

Greenfield was considered a political moderate in a liberal New York City Council.^[21] Greenfield authored a law that banned the Department of Sanitation from placing hard-to-remove stickers on vehicles that were parked on the wrong-side of the street.^[22] He co-authored a law that requires the Department of Education to notify parents and teachers about potentially harmful polychlorinated biphenyl (PCB) in classrooms.^[23] Greenfield also introduced a law that would stop New York City from towing cars for unpaid parking tickets and instead boot the car.^[24] Greenfield's proposed legislation was adopted by the New York City Council Department of Finance as a pilot program in June 2012.^[25] Greenfield was also the author of the Vision Zero legislation that lowers the default speed-limit in New York City to 25 miles per hour. This legislation is the lynchpin of Vision Zero and is widely considered to be the key strategy behind saving lives by reducing traffic accidents in New York City.^[26]

Greenfield voted against a year 2010 bill requiring the New York City Clerks office to post on its website and distribute at its office information on where in the world (countries, jurisdictions, and US States) same-sex gay couples are able to get married.^[27]

Greenfield is a long-time advocate for increased government funding for public and non-public (including religious) schools.^[28]

In July 2017, he announced that he would not be seeking a third term, and would instead be taking over as CEO of the Metropolitan Council on Jewish Poverty.^[29]