In 2012, Senator Borrelli was elected to the Arizona House of Representatives, where he served two terms and was the Chairman of the House Military Affairs & PublicSafety Committee and Vice-Chair of the House Judiciary Committee.

Senator Borrelli was elected to the Arizona State Senate in 2016, where he served as Vice Chair of the Senate Government Committee and later as Chairman of theGovernment Committee. He was also a member of the Appropriations Committee, Commerce & Public Safety Committee as well as the Senate Finance Committee. In December2017, Senator Borrelli was assigned to the Joint Legislative Income Tax Credit Review Committee. In 2018, Senator Borrelli was appointed to serve as a member of theLegislative Council Committee.

In 2020, Senator Borrelli was elected to his 3rd term at the Senate and was again elected by his colleagues as Senate Majority Whip, his 2nd term for this position,where among his duties he presides over Majority Caucus. He is a member on each of the Senate Committees on Government, Commerce, Judiciary and a member of the SenateRules Committee. In 2020, Senator Borrelli was inducted into the Military Rodeo Hall of Fame for his outstanding achievements in Bronc riding and Leadership as the Commissioner of theMilitary Rodeo Cowboys Association from 1988 - 1999.