Before 2008, Plaskett was a member of the Republican Party, and was appointed by President George W. Bush to serve in the Civil Division of the United States Department of Justice.

She was a boarding student at Choate Rosemary Hall, where she was a varsity athlete and served as class president for several years.

She has said that Choate awakened her commitment to public service and a deep sense of responsibility to others through the biblical verse "to whom much is given; much is required".

In 1988, she graduated with a degree in history and diplomacy from the Edmund A. Walsh School of Foreign Service at Georgetown University.

[11] After graduating from law school, Plaskett accepted a position as an assistant district attorney in the Bronx, New York, under Robert T.

She then worked as a consultant and legal counsel focused on internal corporate investigations and strategy for the Mitchell Madison Group.

[12] She left the Committee when she was asked by mentor and fellow trustee at Choate, Robert McCallum, to work at the United States Department of Justice as a political appointee of then-President George W.

[13] While in the Justice Civil Division, she also worked on the Terrorism Litigation Task Force, the September 11th Victim Compensation Fund and United States v. Philip Morris, the case against several major tobacco companies for violations of the Racketeer Influenced and Corrupt Organizations Act (RICO) by engaging in a conspiracy to deceive the public about the health effects of smoking.

[23] In the general election, she faced Republican Gordon Ackley, an Air Force veteran and business owner, who ran as a write-in candidate.

[11] On February 2, 2023, Plaskett was appointed by Minority Leader Hakeem Jeffries as the Ranking Member of the United States House Judiciary Select Subcommittee on the Weaponization of the Federal Government.

[29] Plaskett has criticized multiple decisions made by the Republican majority, saying in her opening statement of the select subcommittee's first hearing, "I'm deeply concerned about the use of the select subcommittee as a place to settle scores, showcase conspiracy theories and advance an extreme agenda that risks undermining Americans' faith in our democracy.

"[30] On March 2, 2023, Plaskett and Judiciary Committee Ranking Member Jerrold Nadler released a staff report titled GOP Witnesses: What Their Disclosures Indicate About The State Of The Republican Investigations, in which they criticized three alleged whistleblowers (George Hill, Garret O’Boyle,[31] and Stephen Friend) who had transcribed interviews with the Select Subcommittee.

In the 315-page report, Subcommittee Democrats doubt the three whistleblowers' credibility, stating that they are heavily MAGA-biased and had no evidence of actual FBI misconduct.