One of five children, Dermody was born in Scranton, Pennsylvania, and raised in nearby Clarks Summit.

[4] To support the family, his mother worked various jobs, including with Capitol Records, the Social Security Administration, and the Pennsylvania Department of Transportation.

[4] After graduating from Abington Heights High School, he received a scholarship to play football at Columbia University in New York City.

[9] In the general election, Dermody faced one-term Republican incumbent Ted V. Kondrich.

[5] In 1994, he was selected by House leaders to lead the investigation into charges against Supreme Court Justice Rolf Larsen, serving as a key House manager (prosecutor) in the impeachment trial that led to Larsen's eventual removal.

In late 2010, he was elected Democratic floor leader on November 17, 2010, after incumbent Todd Eachus was defeated in his bid for re-election.