Polis was seeking a third term against Republican state Sen. Kevin Lundberg in a district where Democrats far outnumbered Republicans.
Polis was first elected in 2008 in the Boulder-based 2nd Congressional District north of Denver. In 2011, the district was redrawn to include Fort Collins, so it now includes both the University of Colorado and Colorado State University.
Polis is the first openly-gay non-incumbent elected to Congress. He favors same-sex marriage rights and is one of the few members of Congress to back marijuana legalization.