McClintock has spent most of his adult life working in the Puerto Rico Legislative Assembly, first as a full-time staffer and subsequently as a legislator, before serving as secretary of state and lieutenant governor. While in college, he was an Amway independent distributor, learning how to run a small private business and earning enough money to support himself. After retiring from government service, he joined Politank*, a government affairs firm as Senior Public Policy Advisor, until 2017 when Senate President Thomas Rivera Schatz recruited him as his senior advisor.