Mark Lamb leads the AZ-05 Republican primary field at 49% in trader consensus, driven by his Trump endorsement secured in late 2025, prior name recognition from his Pinal County sheriff tenure and 2024 Senate bid, and strong early polling that placed him well ahead of rivals. Travis Grantham holds second at 22% on the strength of his legislative record as a former state representative, though his support has not kept pace with Lamb’s momentum. Jay Feely trails at 2.5% amid limited prior political experience. Key recent catalysts include candidate announcements in fall 2025 that crowded the open seat left by Rep. Andy Biggs and subsequent polling and endorsement developments that reinforced Lamb’s position ahead of the July 21 primary.