Colorado's longest-serving congressional Republican faces the biggest primary challenge of his U.S. House career Tuesday.
The primary contest between three-term Rep. Doug Lamborn of Colorado Springs and business Robert Blaha headlines an otherwise low-key state primary Election Day Tuesday.
Lamborn is Colorado's most conservative congressman and among the most conservative in the nation.
Lamborn faces a spirited challenge from Robert Blaha, a deep-pocketed businessman who has plowed nearly three-quarters of a million dollars of his own money into his campaign.
Lamborn is Colorado's only sitting congressman from either party facing primary opposition.
The only other congressional primary is in northern Colorado's 2nd District, where Republicans are jousting for the chance to challenge Democratic Rep. Jared Polis.