[4] He co-led what the Anchorage Daily News called "a cadre of high-powered operatives" described by McCain's campaign as a "truth squad" to field questions about and defend attacks against his running mate, vice-presidential candidate Sarah Palin, the governor of Alaska.

The public face for this pushback, though, will be woman Republican politicians, a 'truth squad' team designed to highlight attacks on Palin and draw sympathy to her side.

[8] O'Callaghan was sent to Alaska to handle "legal issues that are affecting the political dynamic of the campaign," according to Taylor Griffin, a former Treasury Department official in the Bush administration.

[12] In 2011, he joined the law firm Clifford Chance in New York as a Partner in its White Collar, Regulatory Enforcement and Government Investigations practice group.

[19] In 2022, following the publication of Berman's book, the Senate Judiciary Committee opened an investigation into allegations that the Trump administration sought to use the U.S. Attorney's office in SDNY for partisan reasons.

[20][21] The nine-page memo, dated March 24, 2019, was co-written with another senior Trump DOJ official, Assistant Attorney General Steven Engel.

O'Callaghan and Engel asserted that the evidence uncovered by the special counsel investigation led by Robert Mueller was insufficient to support a case for obstruction against Trump.

[20] The watchdog organization Citizens for Responsibility and Ethics in Washington launched a Freedom of Information Act suit against the Justice Department, and the U.S. Court of Appeals for the D.C.