“Texas, in particular, can cause a potential Electoral College-popular vote skew because of its large and growing population. If the Democrat goes from losing Texas by 15 percentage points to losing it by 5 points instead, that produces a net gain of about 0.6 or 0.7 percentage points of the popular vote — larger than the margin by which Al Gore beat George W. Bush in the popular vote in 2000 — without changing the tally in the Electoral College.”