He was the first chairman of the Wisconsin Government Accountability Board, appointed by Democratic Governor Jim Doyle.

In 1986, Deininger launched a primary challenge against three-term incumbent Republican John T. Manske for his seat in the Wisconsin State Assembly.

In the 1984 election, Deininger had worked for Manske's re-election campaign, but declared in 1986 that it was "Green County's turn to be represented in the Assembly."

[1] Only two years later, in 1996, he was appointed to the Wisconsin Court of Appeals by Governor Tommy Thompson to fill the vacancy created by the retirement of Judge Robert D. Sundby.

The Attorney General found that even though Deininger had retired from the Court of Appeals, he was ineligible to serve on the GAB because the term he was elected to had not expired.