For his first six terms, Clay represented the northern two-thirds of St. Louis, while the southern third was in Missouri's 3rd congressional district, represented by Russ Carnahan. After Missouri lost a congressional district as a result of the 2010 census, the final map resulted in the 3rd district being eliminated and the 1st district absorbing all of St. Louis, a decision in which then-U.S. Senator Claire McCaskill said Clay was involved for his self-interest. Clay beat Carnahan in the August 7, 2012, primary, 63% to 34%.