Each dot represents a member of Congress. The \(x\)-axis is dimension 1 of Poole and Rosenthal’s (2017) DW-NOMINATE ideal points, which generally covers issues of socioeconomic welfare; the \(y\)-axis is dimension 2, which generally covers civil rights issues. Members representing states in the South are shown as pink regardless of party affiliation, whereas the dividing lines were only based on party affiliation. The slopes for the dividing lines were computed using linear discriminant analysis, which finds the boundary line that maximizes the separation between the two parties. In most browsers, you can right-click on the graphic and click “Show controls” to enable the pause button and progress bar. If the graphic is not loading, click here to view the raw image. Data source: Voteview (2021).