Katie Arrington
Former South Carolina state representative, two-time SC-01 congressional candidate, and Department of Defense cybersecurity official, twice the Trump-endorsed standard-bearer against Mark Sanford (2018) and Nancy Mace (2022).
Katherine Elizabeth "Katie" Arrington (born December 6, 1970) is a South Carolina Republican, a former state legislator and two-time candidate for South Carolina's 1st Congressional District, and a U.S. Department of Defense cybersecurity official. She is most relevant to the Nancy Mace record as the candidate Donald Trump twice elevated to challenge sitting Lowcountry incumbents, Mark Sanford in 2018 and Mace herself in 2022.
What Happened
South Carolina House (2017-2019). Arrington represented District 94 in the South Carolina House of Representatives for a single term.
2018, beating Sanford with Trump's help. In the June 12, 2018 SC-01 Republican primary, Arrington defeated incumbent Rep. Mark Sanford roughly 50 percent to 46 percent, a result that came hours after Trump endorsed her on Twitter, writing that Sanford was "better off in Argentina" and "I fully endorse Katie Arrington for Congress." She lost the November 2018 general election to Democrat Joe Cunningham by about 1.4 points. (Nancy Mace, then a state representative, had run in that same 2018 primary and did not advance.)
Department of Defense (2019-2021). Arrington left elective politics for the Pentagon, serving as Chief Information Security Officer for Acquisition and Sustainment in the Office of the Under Secretary of Defense, the official behind the department's Cybersecurity Maturity Model Certification (CMMC) initiative.
2022, the Trump-backed challenge to Mace. On February 9, 2022, Trump endorsed Arrington to unseat Mace in the SC-01 Republican primary, payback for Mace's criticism of him after January 6, 2021. Trump called Mace "an absolutely terrible candidate" and praised Arrington as "liked and respected and a true Republican" with his "complete and total endorsement." Mace defeated Arrington in the June 14, 2022 primary, roughly 53 percent to 45 percent. (See Donald Trump for the full arc of that contest, including Mace's Trump Tower video.)
Return to the Pentagon (2025-2026). Under Trump's second administration, Arrington returned to the Defense Department in February 2025 as Deputy Chief Information Officer for Cybersecurity and Chief Information Security Officer, and served as Acting DoD Chief Information Officer from roughly March to December 2025. She departed the department in January 2026 to become Chief Information Officer of the quantum-computing firm IonQ.
Sources
- Wikipedia, Katie Arrington
- CNBC, "Trump endorses Mark Sanford's primary opponent Katie Arrington" (June 12, 2018)
- Ballotpedia, South Carolina's 1st Congressional District election, 2018
- Post and Courier, "Donald Trump endorses Katie Arrington 1 day after she challenges Nancy Mace for Congress" (Feb. 9, 2022)
- Roll Call, "Rep. Nancy Mace defeats Trump-backed challenger Katie Arrington" (June 14, 2022)
- DefenseScoop, "Katie Arrington returns to DoD as CISO" (Feb. 20, 2025)
- DefenseScoop, "Katie Arrington appointed DoD CIO, acting" (March 3, 2025)
- DefenseScoop, "Katie Arrington to be CIO of IonQ" (Jan. 14, 2026)