"The most recent data from the IRS, in 2000, show that the top 5% coughed up more than half of total tax revenue. Specifically, we are talking about folks with adjusted gross incomes of $128,336 and higher being responsible for 56% of the tax take."
Are you meaning the same top 5% that owns 90% of the wealth in this country? 56%/90%=62.22%. That means that the top 5% are only paying 62% of what the average American pays as a fraction of income; the rich are 38% undertaxed *by your own figures*. The American system is regressive, not progressive. The top 5% vote for lower taxes for themselves, for the exact same reasons as you claim that the lower income brackets would vote for higher taxes for other people-- to make the middle class pay for the rich, as they already do.