Notable personal detailsL. John MacKenzie is a Republican candidate for U.S. House in California’s 4th Congressional District in the 2026 cycle. He has described himself as a military veteran, healthcare professional, and small business owner. His campaign states he served 10 years in the U.S. Marine Corps and 15 years in the U.S. Air Force Reserve and has worked on the front lines of healthcare, including with medical and mental health challenges.