Muoio's first elected office that she won was serving on the Pennington Borough Council from 1997 until 2001. In 2000, she was elected to the Mercer County Board of Chosen Freeholders and was re-elected in 2003 and 2006. During her final year on the freeholder board, she served as vice-chair of the freeholder board. In February 2008, County Executive Brian M. Hughes appointed Muoio to become the director of economic development for the county; she resigned her freeholder position upon taking this job. While serving in this position, Muoio was elected to be chair of the Mercer County Democratic Committee in 2010 and was re-elected in 2012 and 2014. After 15th District Assemblywoman Bonnie Watson Coleman was elected to Congress in 2014, Muoio was speculated to become the appointed replacement to her in the Assembly. Muoio and her county committee strongly backed Watson Coleman in the Democratic primary for the Congressional seat in 2014. Though initially other candidates announced intentions to run for the nomination to be appointed to the Assembly seat, members of the Mercer and Hunterdon County Democratic committees unanimously chose Muoio to fill the seat. She was sworn in on February 5, 2015, in the Assembly chamber with her husband, two of her sons, and various local officials present. In the Assembly, she served on the Regulated Professions Committee and the Women and Children Committee. Muoio went on to win in the 2015 general election and started her first full term as assemblywoman the following January. The 15th district consists of most of Mercer County and East Amwell Township, Lambertville, and West Amwell Township in Hunterdon County. The other representatives from the 15th District for the 2018–2019 Legislative Session are Gusciora in the Assembly, while Muoio's Senate colleague is Democrat Shirley Turner. Muoio was nominated by Governor Phil Murphy to serve as the Treasurer of New Jersey. She resigned from the Assembly effective January 15, 2018, as well as from her position as director of economic development for Mercer County in order to begin work inthe executive branch, in advance of her confirmation by the New Jersey Senate; her resignation came less than a week after being sworn into office for her second full term in the Assembly. She was confirmed by the full New Jersey Senate on April 12, 2018.
Personal life
Muoio earned a B.A. in history from Wesleyan University and a J.D. of law from Georgetown University Law School. While at Georgetown, she served as director of constituent services and later as legislative director for TexasCongressmanJack Brooks. She has lived in Pennington with her husband Joseph Muoio since 1995 and has three children. Muoio has served on many boards and commissions including Pennington Borough public commissions, the Pennington Library's board of trustees, and in the Hopewell ValleyLeague of Women Voters.
