Gardner faced Democratic Sen. Brandon Shaffer in Colorado's 4th Congressional District, which included rural eastern Colorado and some areas in Denver's southern suburbs.
He was first elected to Congress in 2010, defeating Democrat Betsy Markey. The 4th District was since redrawn to favor Republicans, making Gardner's re-election chances strong.
Gardner emphasized his family's farming background and said he's a better fit for the rural, conservative district.
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(KUSA-TV © 2012 Multimedia Holdings Corporation with The Associated Press)