[3][4][5] Johnson also served as co-chair of the National Church Arson Task Force alongside former Massachusetts Governor Deval Patrick, chaired the board at the Brennan Center for Justice, co-founded the non-profit group New Jersey Communities Forward and was appointed as the federal affordable housing monitor in Westchester County, New York.

[6][7][8] He formerly served as Corporation Counsel of the City of New York, one of the largest public legal offices in the country, with approximately 1,000 lawyers and 680 support professionals.

He subsequently chaired the Brennan Center for Justice at NYU School of Law,[15] where he worked to protect the right to vote, reduce crime and incarceration and advocated for families facing foreclosure.

Johnson's work led to a revision the law that changed the relationship between state troopers and civilian leadership.

NJCF contributed significantly to the new policies on police worn body cameras, independent shooting reviews and implicit bias training.

[18] He later named his campaign leadership team, which included Doug Rubin, former strategist for Deval Patrick and Elizabeth Warren, Bill Hyers, former campaign manager to Bill de Blasio and John del Cecato, one of President Obama's media strategists.

[22] On January 10, Johnson announced that he was the first candidate to have reached the fundraising threshold necessary to qualify for public matching funds.