Glen B. Gainer III succeeded his own father as West Virginia auditor. Gainer was born on February 26, 1960, in Parkersburg. He earned a bachelor's degree from the University of Charleston in 1982. He worked for four years for the state treasurer's office, three years with the state Department of Energy, and one year in the private sector before running for office. In November 1992, he was elected as the state's 19th auditor, taking over from his father, Glen B. Gainer Jr., who served from 1977 to 1993. Gainer was reelected in 1996, 2000, 2004, 2008, and 2012.

As auditor, Gainer was West Virginia's official bookkeeper, whose job is to ensure the legality of the payment of funds from the state treasurer. The auditor is one of the five constitutional officers who, with the governor, make up the executive branch of West Virginia state government.

In 2009, Gainer discovered and reported suspicious payment activity to federal and state authorities that later proved to be part of an international conspiracy targeting vendors and various state governments. West Virginia has since recovered a portion of the diverted payments and is continuing efforts to recover the remaining $1.5 million.

In 2014, Gainer ran in the general election against incumbent David McKinley to represent West Virginia’s First Congressional District. He lost to McKinley by a roughly two-to-one margin. In May 2016, Gainer left office before the end of his term to become president and CEO of the nonprofit National White Collar Crime Center.

Gainer is married to Susan Ryder, and they have two children. They live in Parkersburg.