Messinger was a delegate to the 1980 Democratic National Convention and served on the New York City Council from 1978 to 1989, representing the Upper West Side of Manhattan. In the City Council, she proposed extending rent control from individuals to businesses. From 1990 to 1998, she served as Manhattan borough president, an office she gave up to unsuccessfully run for mayor in the 1997 election. Her candidacy made her the city's first female Democratic mayoral candidate.[5]
A political liberal, Messinger was known for her advocacy on behalf of public schools, efforts to achieve compromise between developers and neighborhood activists, and her aggressive media work. She is pro-choice and opposes the death penalty. During her 1997 campaign, she was nearly forced into a Democratic primary runoff with Reverend Al Sharpton, but avoided it by receiving 40% of the vote during a recount. She ultimately lost to Giuliani but received more than 500,000 votes.[5]
From 1998 until 2016 she was President and CEO of American Jewish World Service before transitioning to an Ambassador role with the organization.[6]
In late 2005, following a high-profile year that included the Asian tsunami and Hurricane Katrina, The Forward, a Jewish newspaper based in New York City, named her to the top of its annual "Forward Fifty" list of the most influential American Jews. Messinger is also a board member of Hazon and a trustee emerita of the Jewish Foundation for Education of Women.[3] In 2015 she was named as one of The Forward 50.[7]