Klippenstein's journalism career began in
Madison, Wisconsin. By 2018, he was working with
The Young Turks. In 2020, Klippenstein joined
The Nation as their D.C. correspondent. Klippenstein's Twitter account was then suspended, and he reported that the
FBI visited him with "no subpoena, no search warrant, no prior announcement, no claim of illegality". On December 10, 2024, Klippenstein published an alleged
manifesto by
Luigi Mangione, the suspect in
the killing of United Healthcare CEO Brian Thompson; according to
Newsweek, police confirmed his transcription's accuracy. Explaining why he published the manifesto when other media outlets had not, Klippenstein pointed to
paternalistic attitudes in corporate media and the fear of alienating law enforcement sources. Klippenstein published the purported manifesto of
a gunman who shot two Israeli diplomats in May 2025. In 2025, Klippenstein was mentioned in
Donald Trump's lawsuit against
The Wall Street Journal.
Use of the Freedom of Information Act Klippenstein is a self-described "
FOIA nerd"; much of his journalism draws on information he has uncovered from records requested at state and national levels of the US government. His articles also frequently include information from
leaked documents. He obtained leaked documents from the PR firm
Qorvis, which implicated the company pitching the private company
Caliburn on a propaganda video in order to improve the reputation of Caliburn's Homestead, a Florida shelter for "unaccompanied alien children". In an April 2020 article, Klippenstein reported on a leaked document showing that
the Pentagon had warned the
White House in 2017 about the risk of shortages and ill-preparation for a
pandemic brought on by a
novel coronavirus such as
SARS-CoV-2. Klippenstein, along with Talia Lavin and Noelle Llamas, successfully sued the U.S. Immigration and Customs Enforcement. In December, 2020, he filed two new FOIA lawsuits: one against the U.S. Department of Justice, and the other against U.S. Immigration and Customs Enforcement, U.S. Customs and Border Protection, U.S. Department of State, Federal Bureau of Investigation, Defense Intelligence Agency, Office of Intelligence and Analysis, U.S. Department of Energy, Cybersecurity and Infrastructure Security Agency. During the
George Floyd protests, Klippenstein's reporting uncovered documents regarding federal policing of the protests. Specifically, Klippenstein obtained an FBI document that stated the Washington Field Office "has no intelligence indicating
Antifa involvement/presence" during DC-area protests in contradiction to Attorney General
William Barr and other officials' assertions that antifa were specifically responsible for instigating violence. He also reported that contacts working at the
Department of Homeland Security were disgruntled about orders to generate internal intelligence reports on journalists covering protests in
Portland, Oregon as well as participating activists. Later, he co-authored with
Lee Fang an article published by
The Intercept in October 2022 regarding leaked documents exposing Department of Homeland Security's plans to secretly police disinformation online. In response, Klippenstein was interviewed on
Useful Idiots, where he expressed concern about what he saw as a major media failure regarding intelligence information oversight in a situation with no one in control as things drift toward disaster. On August 9, 2023, Klippenstein authored an article published on
The Intercept regarding information Klippenstein obtained via FOIA requests about "[t]he star witness of Congress's UFO hearings,
David Grusch", and Grusch's history relating to
PTSD, depression, suicidal thoughts, and alcohol use. On August 10, 2023, during an interview with
Breaking Points, Klippenstein stated that he spoke with both "
DoD people and intelligence people" while working on his article; Klippenstein described his sources as "mid-level people", who are "experienced, but didn't quite have the political chops generally to quite make it to the top." == Online pranks ==