Morgan's political career began early when political leaders in his home county of Harnett, including highly respected Democratic Party stalwart Venerable Baggett, visited him at the Wake Forest Law School and urged him to run for Clerk of Court. Morgan did so and was elected. After building a reputation in that office, he went into the private practice of law. His skill as a trial lawyer caused his practice to grow, and he soon established a reputation that extended across the state. Personal injury, real property and antitrust law were among his specialties.

He next ran for the North Carolina State Senate and won. He rose to the Senate's highest office, President Pro Tempore, and chaired key committees. He mastered the legislative process, and the experience he obtained in the State Senate served him well when he was later sent to the United States Seante by the voters of North Carolina.

In 1968, Morgan challenged long-time incumbent Attorney General Wade Bruton in the Democratic Party primary, defeated him, and then won the General Election. He served one four-year term and then was re-elected. He served two years of that term and then resigned to run for the U.S. Senate.

Early in his political career, Morgan was considered a conservative because of his allegiance to his former Wake Forest law professor, conservative politician I. Beverly Lake, Sr.. But later, as an influential state senator, as North Carolina attorney general from 1969 to 1974, and as the successful candidate to succeed Democratic U.S. Senator Sam Ervin, Morgan was considered a moderate.

He was defeated for re-election in 1980 by Republican John P. East. Morgan returned to the practice of law and also served as director of North Carolina's State Bureau of Investigation under Attorney General Lacy Thornburg.