Colorado's 4th congressional district is a congressional district in the U.S. state of Colorado. Located in the eastern part of the state, the district encompasses most of the rural Eastern Plains as well as the larger Colorado Front Range cities of Greeley, Longmont, Castle Rock, and Parker. The district is currently represented by Republican Ken Buck. With a Cook Partisan Voting Index rating of R+13, it is one of the most Republican districts in Colorado, especially since the 2012 redistricting removed Fort Collins from the district. No Democrat has received more than 40% of the vote as a US House candidate in the district since 2010.
