There are a couple reasons why switching to chained CPI is a politically convenient way for Republicans to raise money. First, it’s subtle. Most people’s eyes glaze over when they hear about inflation adjustments. And the effect doesn’t become noticeable until years down the road, when people probably won’t even realize they’re paying more taxes than they otherwise would be under the old tax regime. Second, its won’t tick off GOP donors. The richest Americans don’t really need to worry about where tax brackets start and stop, since they pay the top rate on the vast majority of their income anyway. If you make $5 million or $10 million a year, it doesn’t matter if the highest bracket begins $10,000 or even $20,000 lower. As NYU law professor Lily Batchelder summed it up for me, “It’s a stealth tax increase that only affects the non-wealthy and grows over time.”