MY SPIN ON VOTER DEMOGRAPHICS
The analysis all these numbers are based on comes from the 2000 exit polls and is reproduced below (scroll down).
Here's my spin:

Republicans are the party of the self-reliant. The "founder effect" is an important influence on the political parties. The Democrats are the party of Jefferson, an eloquent and idealistic but hypocritical patrician, who aspired to free his slaves but ran up debts his whole life so that when he died his slaves not only could not be freed but had to be sold to pay them off. Democrats remain the party of paternalism, and get the support of the paternalists-- the upper class and the knowledge class-- and the paternalized-- those who want to benefit from welfare handouts (this includes seniors) and affirmative action. Republicans were founded by Abraham Lincoln, the poor country boy, self-educated, who made his way in the world through hard work. The tradition continues: in the 20th century, the greatest Democrat-- Franklin D. Roosevelt-- was another patrician, the greatest Republican-- Ronald Reagan-- was another self-made man.

This self-reliance explains a lot of the demographics. Those with incomes under $15,000 are less likely to be proudly self-reliant. They are likely to get, and to want, help from the public and from others. The upper classes are less self-reliant for a different reason. They have stocks, bonds, properties, real estate, other sources of income than work. And even if they work, they are likely to be high up the hierarchy, entrenched, tenured, secure. But across all classes and income levels, there are people who do not feel self-reliant. People who hold low-paying entry-level jobs may feel dependent on their employers, at whose whim they can be fired. Tenured teachers and government bureaucrats with high levels of job security will feel less self-reliant than self-employed businesspeople with the same income. Men are more likely to (economically) self-reliant than women (housework is a different story-- and forgive me for what may sound like "stereotyping" but these are just facts, whether because of nature or nurture the reader may judge) so they are more likely to vote Republican. Hispanics, so many of whom came here to work hard for a living, are drifting towards the Republicans. If you wanted to test for self-reliance, you would probably ask different questions than these exit polls do. But the explanation works better than the "Republicans are the party of the rich" canard.

By the way, this self-reliance idea is not just another way of saying, Republicans good Democrats bad. Self-reliance is always a half-truth anyway: the truth is, we all need community, we rely on each other, and we rely on the government, too, to maintain law and order and public services, to promote the advance of science, to macro-manage the economy, to provide at least an implicit social safety net (no democracy has ever suffered a famine, as Amartya Sen has shown), to provide a currency, to do some very complicated things like protect intellectual property rights, and to provide public space, streets and parks and national forests. Still, the tax dollars to support all this come from those millions of self-reliant Republicans, and we would all be poorer if high taxes for the sake of "enlightened" spending turned people who work hard for a living into suckers. Most European countries, and we ourselves thirty years ago, did do this to some extent. And it did make us all poorer, and in many cases it was not even the rich who suffered most. The rise of the welfare state ran parallel to the growth of the underclass.

I suspect that a lot of poor people intuit that they will be better off morally and economically by achieving even a meager self-reliance than by receiving government handouts. That's why so many people in the lower income brackets-- probably a majority, I suspect, if we leave aside blacks who are influenced by the legacy of Dr. King-- vote for George W. Bush.