Sean Thomas Casten (born November 23, 1971 in Dublin, Ireland) is a businessman, scientist and politician serving as the U.S. representative for Illinois's 6th congressional district. The district covers portions of five counties in Chicago's western suburbs, including Wheaton, Palatine, and Barrington. Casten announced his candidacy for the United States House of Representatives in Illinois's 6th congressional district in September 2017. He defeated six other contenders in the 2018 Democratic primary to become the party's nominee against six-term incumbent Republican Peter Roskam. On November 6, 2018, Casten won the election, defeating Roskam by a margin of seven points. This race was viewed as one that Democrats needed to win in order to regain control of the U.S. House of Representatives for the first time since the 2010 elections.