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Peter Roskam was a Republican member of the U.S. House of Representatives for Illinois's 6th congressional district. He was first elected in 2004, and was re-elected six more times, defeating Democrat candidates in each election. In 2018, however, Roskam was defeated by Democrat candidate Sean Casten. This was a major upset, as Casten was a political newcomer and Roskam had a large war chest.