Here's visual evidence that gerrymandering has led to substantive differences in the racial composition of Democratic and Republican congressional districts. The typical Democratic district has twice as many Hispanics, Blacks and Asians and about 1/3rd fewer Whites. This helps explain what drives differences between the parties in the House of Representatives. They represent substantively "slices of the country."
What's more, the votes they cast are subject to review by primary voters in their districts. Since primary voters are more extreme ideologically than general elections voters, representatives must placate those voters if they want to stay in office. The Dish argues that this points out that
gerrymandering incentivises members of Congress to polarize.
