He has written or edited 21 books, including two best sellers, Who Runs Congress? (1972) and The Book On Bush (2004). He has collaborated on published works several times with consumer advocate Ralph Nader.
He served as New York City Consumer Affairs Commissioner (1990-1993). As a politician, he was twice elected Public Advocate of New York City (1994-2001). He also won Democratic primaries for the U.S. House of Representatives, U.S. Senate, and Mayor of New York, but in each case lost in the general election.
Green has been married to Deni Frand, a former director of the New York City office of liberal interest group People for the American Way, since 1977. They have two children, Jenya and Jonah. Green's brother is real estate developer Stephen L. Green.
Green's first run for office came in 1980 when he sought to represent the East Side of Manhattan in the House of Representatives. He won a contested Democratic primary but was then defeated by the Republican incumbent, Bill Green (not a relative).
In 1981, Mark Green founded the New Democracy Project, a public policy institute in New York City, which he ran for 10 years. During the 1984 presidential election, he served as chief speechwriter for Democratic candidate Senator Gary Hart, who ran second in the primary.
Green returned to the candidate's role in 1986 when he ran for the U.S. Senate. He was opposed for the Democratic nomination by multimillionaire John Dyson. Although Dyson outspent Green 10-1, Green won the primary. Dyson remained on the ballot as the candidate of the Liberal Party. The race was won by the Republican incumbent, Alfonse D'Amato, who was re-elected.
From 1990 to 1993, Green served as Consumer Affairs Commissioner of New York City. He was elected the first Public Advocate of New York City in 1993 and was re-elected in 1997. In that office, Green led investigations of HMOs, hospitals, and nursing homes which led to fines by the New York State Attorney General. A 1994 investigation on the Bell Regulations ("Libby Zion Law") -- limiting resident working hours and requiring physician supervision -- and follow-up study prompted the New York State Department of Health to crack down on violating hospitals and also launched a series of exposes and legal action against tobacco advertising to children that culminated in the FTC forcing the end of Joe Camel ads.
One of Green's most high-profile accomplishments as Public Advocate was a lawsuit against the unpunished racial profiling in Rudy Giuliani's police force. As Green told the Gotham Gazette, "I sued Mayor Giuliani because he was in deep denial about racial profiling and police misconduct that went unpunished. I won my lawsuit, I released an investigation showing a pattern of unpunished misconduct ... [and] the rate that police with substantiated complaints are punished went from 25 percent, up to 75 percent." Green was one of the first politicians to draw attention to this problem, and for this and other accomplishments in this area he was, until 2001, one of the most popular white politicians among New York City African Americans.
Green ran for the U.S. Senate again in 1998, when D'Amato was seeking a fourth term. Green finished third in the Democratic primary behind the winner, Congressman Charles Schumer, and 1984 Democratic vice presidential nominee Geraldine Ferraro.
Despite Green's ties to Nader, he did not support Nader's presidential campaigns. In 2000 he praised Nader's work as a consumer advocate but he endorsed Democratic nominee Al Gore. In 2004, Green was the co-chair of the New York wing of Senator John Kerry's failed presidential campaign.
Green was roundly criticized for the actions of supporters that were construed as racist, involving literature with New York Post caricatures of Ferrer and Al Sharpton distributed in white enclaves of Brooklyn and Staten Island. Green stated that he had nothing to do with the dissemination of the literature. An investigation by the Brooklyn District Attorney came to the conclusion that "Mark Green had no knowledge of these events, and that when he learned of them, he repeatedly denounced the distribution of this literature and sought to find out who had engaged in it." Nevertheless, the incident is thought to have diminished minority turnout in the general election and helped the Republican candidate win in an overwhelmingly Democratic city. (Village Voice columnist Peter Noel wrote that "Mark Green ... may have replaced [Giuliani] as the most hated white man in the African American community," an ironic twist for someone who had been so popular in that community for so long.)
The September 11, 2001 terrorist attacks occurred on the morning of the Democratic primary and also contributed to Green's loss, since the media barely covered the subsequent general election, and Bloomberg spent $74 million on TV ads and direct mail. The hugely popular Rudy Giuliani — who suddenly had an extremely high popularity rating even amongst minorities — publicly endorsed Bloomberg.
Additionally, Green made a controversial decision during the primary to support Giuliani's unprecedented attempt to extend his own mayoral term, in the name of the emergency of 9/11. Ferrer opposed Giuliani's ultimately unsuccessful attempt at term self-extension, and was able to accuse Green of being rolled over by Giuliani.
The Economist wrote, "The billionaire businessman [Bloomberg] is usually seen as one of the post-September 11th winners (if such a word can be so used): he would probably have lost the mayoralty to Mark Green, a leftish Democrat, had the terrorist strike not happened. Yet it is also worth noting that his election probably spared New York city a turbulent period of score-settling over Rudy Giuliani's legacy.
On September 12, 2006, Green lost to Andrew Cuomo in his bid to secure the Democratic nomination to succeed then-Attorney General Eliot Spitzer. On the evening the results came in, he vowed to reporters that "I won't be running for office again. But I'll continue to advocate, write and teach."