Herlihy was the State Senator for the 8th Senatorial District from 1999 to 2009, representing the northwest suburbs of Hartford in the Farmington Valley and Litchfield County in the Connecticut Senate, including the towns of Avon, Barkhamsted, Canton, Colebrook, Granby, Hartland, Harwinton, New Hartford, Norfolk, Simsbury, and Torrington.

He taught in the Simsbury School District and then worked in the insurance business.

[1] In 1997, he became the State Representative for the 16th Assembly District, a position he held until his election to the Senate.

While at the General Assembly, Senator Herlihy was honored by the Connecticut State Firefighters Association for spearheading efforts to provide thermal imaging equipment for fire departments throughout Connecticut.

After retiring from the Senate after five terms, Herlihy was once again re-elected to the Board of Selectmen on November 3, 2009.