Mark Lamb (R) defeated Daniel Keenan (R) in the Republican primary for Arizona's 5th Congressional District on July 21, 2026. Incumbent Rep. Andy Biggs (R), who was first elected in 2016, ran for governor of Arizona rather than for another term.

Keenan led in fundraising, while Lamb led in noteworthy endorsements.

As of July 1, 2026, Keenan raised $1,851,302 to Lamb's $1,222,217. 

In terms of noteworthy endorsements, President Donald Trump (R), Speaker of the House Mike Johnson (R-La.), Rep. Eli Crane (R-Ariz.), and Rep. Paul Gosar (R-Ariz.) endorsed Lamb. As of July 21, 2026, Keenan has not announced any endorsements.

Both candidates have similar policy positions and identify as constitutional conservatives. They also campaigned on how their careers have prepared them to serve in the U.S. House.

Lamb served as sheriff of Pinal County from 2017 to 2025. He previously worked in law enforcement at the Salt River Police Department and the Pinal County Sheriff's Office and owned a pest control business. In 2024, Lamb unsuccessfully ran for the U.S. Senate in Arizona. Kari Lake (R) defeated Lamb in the Republican primary 55% to 40%.

According to Lamb's campaign website, "[H]e witnessed firsthand the consequences of illegal immigration, cartel activity, drug trafficking, human smuggling, and violent crime. While politicians debated the issues, Mark and his deputies faced them every day on the front lines."

Keenan is the founder of DK Builders, a residential construction company. His previous career experience included working as a forklift operator in a warehouse and agricultural work.

According to Keenan's Candidate Connection survey, "His experience overcoming economic challenges has reinforced his commitment to conservative principles of fiscal responsibility, limited government, and strong community values. Today, Daniel is running for Congress to bring these values and his real-world experience to Washington, DC."

As of July 21, 2026, The Cook Political Report with Amy Walter and Inside Elections with Nathan L. Gonzales rated the general election as Solid Republican. Larry J. Sabato's Crystal Ball rated it as Safe Republican.