[2] After graduating from law school, Clark clerked for Judge Danny J. Boggs of the United States Court of Appeals for the Sixth Circuit (Cincinnati, Ohio).

[22] In June 2017, Clark was nominated by President Donald Trump to become the United States Assistant Attorney General for the Environment and Natural Resources Division.

[24] Within the division, Clark "developed a reputation for pushing aggressive conservative legal principles and taking a hands-on approach that drew kudos from some colleagues but often frustrated career lawyers on his team.

"[27][28] While Assistant Attorney General, Clark tried to delay the DOJ in seeking criminal and civil charges against North Dakota pipeline operator Summit Midstream Partners for its role in the largest-ever inland spill of waste water from oil drilling.

[22] In late December 2020 and early January 2021, Clark tried unsuccessfully to get the Justice Department to support Trump's attempts to overturn the results of the 2020 presidential election.

The letter suggested the Georgia legislature should "call itself into special session for [t]he limited purpose of considering issues pertaining to the appointment of Presidential Electors".

He claimed intelligence community analysts were withholding information, saying he had heard that "a Dominion machine accessed the Internet through a smart thermostat with a net connection trail leading back to China.

Clark further noted that he had been the lead signatory on the Justice Department's letter opposing a claim that Vice President Mike Pence had the power to reject electoral votes for Biden when Congress met to certify the result.

"[41][42] In early August, Rosen and Donoghue told the inspector general and members of the Senate Judiciary Committee that Clark helped Trump attempt to subvert the election.

[47] They "reveal that we were only a half-step away from a full-blown constitutional crisis as President Donald Trump and his loyalists threatened a wholesale takeover of the Department of Justice (DOJ).

They also reveal how former Acting Civil Division Assistant Attorney General Jeffrey Clark became Trump's Big Lie Lawyer, pressuring his colleagues in DOJ to force an overturn of the 2020 election.

According to Clark's boss at the Center for Renewing America, Russell Vought: "DOJ law enforcement officials ... put him in the streets in his pajamas, and took his electronic devices.

"[52] The search came one day before the House Select Committee on the January 6 Attack held a televised hearing that addressed Clark's alleged role in attempts to overturn the 2020 United States presidential election.

[53] Media Matters reported the next day that in May 2022 Clark promoted the disproven Dinesh D'Souza film 2000 Mules while taunting law professor Steve Vladeck and Democratic elections attorney Marc Elias on Twitter.

He asked Elias, who had thwarted every lawsuit Trump's legal team had pursued after the election, "Were you part of the massive multi-State operation #TrueTheVote uncovered?

Despite this, Clark directed Kenneth Klukowski, who joined the Justice Department after the 2020 presidential election, to conduct research on submitting unauthorized electors to Congress.

[8] Clark was allegedly warned by the Deputy White House Counsel that should Trump refuse to leave office there would be "...riots in every major city in the United States," according to the indictment.

[63] In October, after Clark received a congressional subpoena regarding his participation in the January 6 attack on the Capitol, his name disappeared from the NCLA site, though it had been restored by the time of his indictment.