Surprise! It's the wealthy! Here's TaxVox:
TPC's Katherine Lim has crunched some numbers on John McCain's proposal to temporarily cut capital gains tax rates from 15 percent to 7.5 percent. In 2009, under a plan that lowers taxes on both gains and dividends, those making $1 million or more would get two-thirds of the benefit, and an average tax cut of more than $72,000. Those making less than $50,000 would get, on average, nothing.
The man who stood strong (and largely alone) against the Bush tax cuts because they disproportionately benefited the wealthy is suggesting making our tax code less progressive. Here are the numbers used in the calculations, and here is more on McCain's newly proposed economic policies.