In January 2025, President Donald Trump nominated Steinhardt to be the United States Attorney for the District of New Jersey.

[5] He was also a four-year member of the Gettysburg NCAA Division III football team, as well as a brother of the Phi Delta Theta fraternity.

[8] In his first run for public office, Steinhardt was elected Mayor of Lopatcong Township in 1999, beating Democratic incumbent William Baker by twelve votes.

[17][better source needed] Steinhardt was elected chairman of the Warren County Republican Committee on January 31, 2004, to fill the unexpired term of the outgoing chair who resigned to focus on private sector opportunities.

He defeated his opponent by a 2–1 margin among elected members of the committee[18] According to the Express Times his leadership style and ability to bring various factions of the party together made it so that he ran unopposed for a full term six months later.

[23] Six months later in November 2017, after the Democratic victory in the ensuing gubernatorial election, Lavery resigned and Steinhardt was named chairman.

[33] In January 2017 Steinhardt co-founded and co-chairs the Warren County Addiction Awareness Task Force to address the spiraling heroin and opioid epidemics.