Former Pinal County Sheriff Mark Lamb will run for the East Valley-area congressional seat being vacated by U.S. Rep. Andy Biggs.

Lamb will officially announce his candidacy Oct. 22, he told The Arizona Republic.

Lamb, 53, is so far the biggest name in what has become a crowded GOP primary in Arizona's 5th Congressional District, which includes parts of Gilbert, Chandler, Queen Creek and Apache Junction.

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