[8] Mangi began his career as an associate at Patterson Belknap Webb & Tyler in New York City in 2000, becoming counsel in 2009; he was elevated to partner in 2010.

[14] Following the vacancy left by retiring judge Joseph A. Greenaway Jr. in June of 2023, President Joe Biden announced his intent to nominate Mangi to serve as a United States circuit judge of the United States Court of Appeals for the Third Circuit on November 15, 2023.

[24][25][26] A month later, the Washington Examiner reported that in his Senate Judiciary Questionnaire Mangi had failed to include that he moderated a panel at the National Association of Muslim Lawyers annual conference in 2022.

[29][30] Democratic senators Catherine Cortez-Masto, Joe Manchin and Jacky Rosen soon announced their opposition to his nomination.

[31][32][33] In April 2024, in response to what they asserted was an Islamophobic reaction to Mangi's nomination, more than 100 public policy, labor and advocacy organizations, including the American Federation of Labor, the Center for American Progress, and the NAACP, collectively wrote a letter to the Senate asking members to confirm Mangi.

[36] Journalist Lydia Polgreen authored an op-ed in The New York Times entitled "The Islamophobic Smear Campaign Dividing Democrats.

A Republican-appointed former Judge of the Third Circuit, Tim Lewis, also wrote to Senators and spoke out to condemn the attacks on Mangi and urge his confirmation.

Talk show host John Oliver devoted a segment to the attacks on Mangi as part of an exploration of Islamophobia in America where he described the attacks as “yet more six degree of separation nonsense.”[41][42] On May 17, dozens of major law firm partners and counsel working on pro bono issues wrote a letter to Senate leaders decrying what they identified as a smear campaign against Mangi that, if successful at derailing the nomination, would tend to deter pro bono involvement by would-be federal judicial candidates.