Arizona held a popular vote for its United States Senators (and future state officers) on December 12, 1911 prior to being admitted at the 48th state, which eventually occurred on February 14, 1912. There was a single ticket for both seats. The results here are for the second highest candidates from each party. Marcus Smith assumed Arizona's Class 3 Senate seat, which would next be up for election in 1914. The results for the Class 1 seat are listed separately as a regular election in 1911.
This popular vote for United States Senator was technically only an advisory vote as prior to the adoption of the 17th Amendment in 1913, state legislatures officially elected United States Senators. The newly constituted Arizona Legislature unanimously chose Marcus Smith (and Henry Ashurst) as its first United States Senator on March 27, 1912. Arizona became the second state to ratify the 17th Amendment, doing so on June 3, 1912.
Source for Popular Vote data: Arizona Secretary of State. Official Returns for General Election, December 12, 1911, Arizona Secretary of State (https://azmemory.azlibrary.gov/nodes/view/282121) (accessed 17 Nov 2023)