The Española native was an aide to U.S. Sen. Joseph Montoya, D-N.M., 1975-77; cabinet secretary of the state Department of Labor, 1977-81; and a member of the state Corporation Commission, predecessor of the Public Regulation Commission, 1981-98.
In 1997, Serna was the Democratic nominee for the 3rd Congressional District seat vacated by Bill Richardson so he could serve as U.S. ambassador to the United Nations. (Richardson later became head of the U.S. Department of Energy.) After losing to Republican Bill Redmond in a special election, Serna became regional outreach coordinator for the U.S. Department of Agriculture from 1998 to 2000.
In 2001, he was appointed state insurance superintendent, a job paying more than $90,000 a year. He was the founding president of the Con Alma Health Foundation, created the same year from the sale of Blue Cross and Blue Shield of New Mexico. He resigned as insurance superintendent in 2006 amid charges he dismissed fines on insurance companies that donated to Con Alma and other nonprofits.