Like I say, your little theory works in some places and doesn't work in others. It's like saying the stock market goes up more on average in years where the NFC team wins the Super Bowl than in years when the AFC team wins. True, but the Super Bowl has nothing to do with the stock market. Just about as bogus as your population theory. (Suburban Atlanta votes far more conservative than many rural Georgia areas which are still overwhelmingly Yellow Dog Democrat). Surely Bush wasn't in a close election because he was running against the Vice President of an administration that was sitting on top of the best economy in the history of the world, right?
You can also point to cases where someone fell from a great height--yet suffered hardly a scratch.
That doesn't change the fact that it is wise to avoid falling.
To discover a trend, you don't just look at one or two examples, you look at all and average them out.
Which I did for you above.
And the difference in population densities was glaringly obvious.
The trend is that the greater the population density of a place, the more liberal the place.