My research suggests that this combination of political “sorting” and changing white perceptions of the Democratic Party has resulted in an almost eight-point swing in white vote choice. That lines up well with actual vote returns. White votes were split between the two parties about 50-50 in the 1970s — but in elections since 2000, that has become closer to 60-40 in favor of the Republican Party. Democrats might be gaining more votes from Latinos, Asians and other emerging demographic groups, but they are losing whites as a result.
Furthermore, the demographics of the white voters who are likely to support Democrats are different from the white voters who supported the Democratic Party in previous decades.
Most notably, while the Democratic Party is winning a lower percentage of whites overall, a greater proportion of college-educated whites are voting for Democrats. Attitudes on social issues in particular have become stronger predictors of voting behavior in recent elections; economic attitudes have become more important, too, but were already quite a strong predictor to start with.