To "flip" a congressional seat refers to the process of changing the party affiliation of a congressional district from one political party to another during elections. This typically means that a candidate representing a different party successfully defeats the incumbent, which often indicates a significant shift in voter sentiment or demographic changes in the district. Flipping seats can impact the overall control of Congress, thereby influencing legislative agendas and the balance of power. This phenomenon is common during midterm elections when opposing parties often capitalize on the ruling party's perceived shortcomings.