Eldridge was elected to serve as State Representative on November 5, 2002. Upon his election to the state legislature, Eldridge became the first elected official in the history of Massachusetts to be elected as a Clean Elections candidate. To date, he remains the only such elected official, as the Massachusetts Clean Elections law was repealed a little over a year later. He was first sworn in as state representative on January 1, 2003, when he cast his first vote in the Speaker of the House election for Byron Rushing over Thomas Finneran. The district included the towns of Acton (precincts 3, 4, & 5), Boxborough, Harvard, Lancaster (precinct 1), Lunenburg, and Shirley. As a result of the represented towns in this new district, Rep. Eldridge represents many of the residents of the Devens community, a former U.S. military base now run by the state.