The district is currently vacant and was last represented by RepublicanKen Buck. With a Cook Partisan Voting Index rating of R+13, it is the most Republican district in Colorado.[4] No Democrat has received more than 40% of the vote as a U.S. House candidate in the district since 2010.
Following the 2010 U.S. census and associated realignment of Colorado congressional districts, the 4th congressional district consisted of Baca, Bent, Cheyenne, Crowley, Elbert, Kiowa, Kit Carson, Las Animas, Lincoln, Logan, Morgan, Otero, Phillips, Prowers, Sedgwick, Washington, Weld and Yuma counties. The district also includes portions of Adams, Arapahoe, Boulder and Douglas counties and very little portions of Larimer County.
This district consists mainly of the area of Colorado that is part of the Great Plains region of the United States. It is largely rural. The only large populated places in the district are Loveland, Highlands Ranch, Castle Rock, and Parker. Until the 2010s redistricting, Fort Collins was the largest city in the district and provided a large Democratic base, making the district somewhat competitive: before the 2020 redistricting, Greeley was the largest city in the district but has since been moved to the 8th district.
While the 4th takes in some suburbs of the Democratic-leaning Denver metropolitan area, the 4th takes in Douglas County, the most Republican region in the area. However, it is still far more friendly to the Democrats than the other counties in the district (especially in blue-leaning Highlands Ranch and Lone Tree) and is the only area in the district with any Democratic support of real significance. On the other hand, the district takes in some of the most Republican counties in Colorado, such as Washington, Kit Carson, and Logan, where Democrats rarely exceed even 20 percent of the vote.
Historically, the district has been Republican-leaning, though Marilyn Musgrave won relatively narrow victories in 2004 and 2006 due to her Democratic opponents' strength in Fort Collins. Musgrave had to rely on strong performances in more conservative Greeley to hold onto her seat. In 2008, Musgrave lost reelection to Betsy Markey, who became the first Democrat to represent the district since the early 1970s. Markey was defeated in 2010 by Republican Cory Gardner, and the district was made more Republican in redistricting due to the removal of Fort Collins; no Democratic nominee has won more than 40% of the vote since she left office.
George W. Bush received 58% of the vote in this district in 2004. John McCain narrowly carried the district in 2008 with 50% of the vote.
