These mix effects are what people typically have in mind when they think of the pro-Democratic effects of rising diversity (now generational succession). But mix effects, by definition, assume no shifts in voter preference: they are an all-else-equal concept. If voter preferences remain the same, then mix effects mean that the Democrats will come out ahead. That is a mathematical fact.

But voter preferences do not generally remain the same (see #4). We have seen this in the case of rising nonwhite voter share, as white working-class voters moved toward the Republicans and, more recently, nonwhite voters themselves have become more Republican. This has cancelled out much of the presumed benefit for the Democrats from the changing racial mix of voters. …

In short, there’s no free (demographic) lunch. The boring, tedious, difficult task of persuasion is still the key to building electoral majorities.

[I’m amused by the fact that Dems are relying on a youth vote to re-elect an 82-year-old man whose age and cognition are obvious issues, and whose speeches are marked more often with fabulist ramblings and incoherent passages. Republicans have a real opportunity to offer a youth-oriented contrast. — Ed]