Is it fact that Fort Collins was taken out of Colorado's 4th Congressional District?
Over at Wikipedia, for Congressman Cory Gardiner (R-Yuma), the map of Colo. #04 still shows Fort Collins as part of that district.
That's the map of the old district. For the new CO-4, Larimer County was removed from the district and put in CO-2, while the new district picked up heavily republican Elbert County and most of similarly heavily GOP Douglas County, which had previously been part of CO-6 (Tom Tancredo's old district.)
As a result, the new district is way more republican than the old one. Obama came within a point of winning the old one in 2008, but would have lost the new one that same year by fourteen and a half points. Romney carried it in 2012 with nearly sixty percent of the vote.