- The doorbell chimed "The Star Spangled Banner" as retired Col. Lou Christensen stepped inside the large house on the northeastern edge of Colorado Springs.

The registered Republican and 28-year Air Force veteran was doing something he never expected to do - attending a party for a Democratic congressional candidate.

"The legislative branch needs to put up guardrails from President Trump," said Christensen, 70. "We need another branch of government that stands up and says, 'Uh, boss, that's not constitutional.'" Christensen is backing Jessica Killin, a fellow veteran, over first-term Republican Rep. Jeff Crank in Colorado's 5th Congressional District, a conservative stronghold that includes five military facilities.