One measure of change in the electorate is the performance of Republican presidential candidates in the 15 largest counties in 1988 and 2016. On average, GOP performance dropped about 19 percent.
| 1988 | 2016 | ||
| Los Angeles CA | 46.90% | 22.40% | -24.50% |
| Cook IL (Chicago) | 43.40% | 20.80% | -22.60% |
| Harris TX (Houston) | 57.00% | 41.60% | -15.40% |
| Maricopa AZ (Phoenix) | 64.90% | 47.70% | -17.20% |
| San Diego CA | 60.20% | 36.60% | -23.60% |
| Orange CA | 67.70% | 42.30% | -25.40% |
| Miami Dade FL | 55.30% | 33.80% | -21.50% |
| Kings NY (Brooklyn) | 32.60% | 17.50% | -15.10% |
| Dallas TX | 58.40% | 34.30% | -24.10% |
| Riverside CA | 59.50% | 44.40% | -15.10% |
| Queens NY | 39.70% | 21.80% | -17.90% |
| Clark NV (Las Vegas) | 56.40% | 41.70% | -14.70% |
| King WA (Seattle) | 44.80% | 21.00% | -23.80% |
| San Bernardino CA | 60.00% | 41.50% | -18.50% |
| Tarrant TX | 61.20% | 51.70% | -9.50% |
| -19.26% |
