Mick McGuire is adding his name to the growing list of Arizona Republicans vying to challenge Democratic Sen. Mark Kelly in the midterm elections.

McGuire, former adjutant general of the Arizona National Guard, was to announce his candidacy on Tuesday. He joins wealthy businessman Jim Lamon in a Republican primary that is expected to expand by at least one in July with the addition of Blake Masters, who works in venture capital with GOP megadonor Peter Thiel. Arizona Attorney General Mark Brnovich could also run.