Chained CPI has for years been "a potential sop to conservatives".

[The Magistrate]

11. The Whole 'Substitution' Line Is Utterly Bogus, Ma'am

If the price of some articles rise, and a person therefore purchases different items in substitution, at lower cost and of lower quality, while that person may be paying about the same amount, they are getting less value for it, and therefore their standard of living has not kept pace with rising costs. The purpose of a cost of living index is to maintain the standard of living of persons receiving income, or, in other words, to see that they can buy the same items they did formerly, when the cost of those items rises. Put even more coldly, the purpose of a cost of living index is to see to it people get the same value from their income as they did formerly when prices rise. The 'substitution' line is an open statement that the value people will receive for their income will drop as the price of goods rises. The people pressing this do not even try to hide it, save by leaving it in plain sight and trusting people will not look and see....