Retired Air Force Col. Martha McSally will face Democratic Rep. Ron Barber in southern Arizona's 2nd District.
McSally beat out little known challenger Mark Koskiniemi in Tuesday's primary.
Barber won Gabrielle Giffords' seat in a June special election against Republican Jesse Kelly. Republican McSally ran in April's special primary election and came in second to Kelly.
Barber was challenged by state Rep. Matt Heinz. Other Democrats backed out after Giffords announced she was resigning and endorsed Barber as her replacement early this year.
The 2nd District takes in parts of Tucson and Pima County and all of Cochise County.
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