He was appointed to the position by Governor James R. Thompson after the incumbent, William Scott, had been convicted of a tax crime, which disqualified him from office.

[4] Fahner ran for a full term as attorney general, but was defeated by Democratic candidate Neil Hartigan in the 1982 election.

[4] After leaving office in 1983, Fahner returned to private practice, joining the law firm Mayer Brown LLP as a partner.

[7] In 2015, Fahner wrote a letter to U.S. District Judge Thomas M. Durkin urging a lenient sentence for former House Speaker Dennis Hastert, who had pleaded guilty to unlawfully structuring bank withdrawals to avoid reporting requirements.

)[8] Fahner referred to Hastert as "a kind, strong, principled, and unselfish man" and wrote: "I urge the court to permit him to live the rest of his life in freedom with his family and friends, and all those who love and admire him.