Incumbent Sen. Martha McSally defeated Daniel McCarthy and write-in candidate Sean Lyons in the Republican special primary election for U.S. Senate in Arizona on August 4, 2020.
The special election was called to fill the rest of the 2017-2022 term that John McCain (R) was elected to in 2016. McCain died of cancer on August 25, 2018. Gov. Doug Ducey (R) appointed Jon Kyl (R) to the seat in 2018, and Kyl resigned later that year. Ducey then appointed McSally.
Prior to her appointment, McSally ran for Senate in 2018 and lost to Kyrsten Sinema (D) 47.6% to 50%. McSally served in the U.S. House of Representatives from 2015 to 2019. During the primary, she highlighted her military service and said she would work to protect coverage for people with pre-existing conditions, lower prescription drug costs, and hold China accountable for the COVID-19 pandemic.