A judge by profession, he has had a long career as a jurist. In 1979 he was appointed to the Supreme Court of Mainland, becoming the Chief Justice of Mainland in 1996. In 2000, when the state divided, he became the Chief Justice of East Mainland. In 2004, when Governor Charlotte Lang left office to become President of Georgeland, McClellan became Acting Governor under the East Mainland constitution, and was elected Governor by a margin of 9% over his opponent, David Hurst, at the special election held in August of that year. At the next election, held in 2006, McClellan was defeated by Hugh St. Clair.
Former Governor McClellan died on October 31, 2006, of a stroke. He had suffered a stroke while in office, but the condition was minor and he recovered. On October 28, 2006, he suffered a much more serious stroke. Initially his prognosis improved, but he died three days later in St. Peter's Hospital in Lylecity.