Maguire served on the Health and Environment, Energy, and Oversight subcommittees of the House Commerce Committee and helped found the New Members’ Caucus.

In Congress, he worked on: In 1980, Maguire was defeated by Republican challenger Marge Roukema and in 1982 ran as a candidate for nomination to the United States Senate, falling short by 11,788 votes and placing second to Frank Lautenberg in the 10-candidate New Jersey Democratic primary election.

As an independent consultant from 2003 to 2006, he advised corporate and public sector clients on domestic and international business development, job creation, and marketing initiatives.

In that role, he helped advance the global alliance's goal to ensure that "every child everywhere" is immunized against life-threatening diseases with a focus on the world's 75 poorest countries.

In 2012, Maguire was approached by local Democratic Party leadership in New Jersey's 5th congressional district about challenging GOP incumbent Scott Garrett in 2014.