Former Pinal County Sheriff Mark Lamb dominates trader consensus at 89.5% implied probability to win Arizona's 5th Congressional District Republican primary on July 21, driven by President Trump's November 2025 endorsement, Club for Growth backing, and a December 2025 poll showing his massive lead among likely GOP primary voters in this R+10 open seat left by Rep. Andy Biggs. State Rep. Travis Grantham's March 12 suspension of his campaign for active Air National Guard duty—cleared the field just before the April 6 filing deadline—further consolidated support for Lamb, whose signature submission secured his ballot spot. Former NFL kicker Jay Feely trails at 2.7% after switching to AZ-01 late last year. Late scandals or surges by minor candidates like Daniel Keenan could shift odds, though Lamb's name recognition and conservative credentials maintain his edge.