Mark Lamb, the former Pinal County sheriff, won Arizona’s 5th Congressional District Republican primary on July 21, capturing 58.7% of the vote against self-funded challenger Daniel Keenan, who received 41.3%, according to results reported by Politico. Lamb will advance to November as the heavy frontrunner in the deep-red Phoenix-area district to replace Rep. Andy Biggs, who is running for governor.
Lamb served as Pinal County sheriff from 2017 to 2024 and became known nationally as a vocal critic of the Biden administration’s immigration policy. He secured President Donald Trump’s endorsement for the House race last year and Trump reinforced that backing in mid-July, according to Politico.
The primary was contentious. Keenan, a self-funding candidate, poured nearly $2 million of his own cash into the campaign in an attempt to make Lamb’s alleged sexual misconduct the central issue of the race, per Politico. In May, the Arizona Republic had published a multi-part investigation alleging that Lamb engaged in a yearslong pattern of sending sexual images and instigating intimate encounters involving him, his wife, and others. Lamb has denied the allegations, with his spokesperson telling Politico that “these allegations are false and come from long-discredited political opponents.”
Despite the controversy, Lamb did not lose any significant endorsements. His victory underscores the continued strength of Trump’s political backing in Republican primaries. According to Ballotpedia, candidates endorsed by Trump won 220 of 227 races (97%) in 2026 primaries so far—a success rate that reflects how closely GOP primary voters align with the president’s preferred candidates.
Sources
- Politico — Lamb’s primary victory, vote totals, Keenan’s spending, and details of the allegations and Trump’s endorsement
- Ballotpedia — Trump’s 2026 primary endorsement success rate (220 of 227 wins, 97%)
- A&E — Lamb’s tenure as Pinal County sheriff from 2017
