If I was a Democrat in Congress, I would try and get the GOP to sign onto the chained-CPI for the tax code. In exchange, I'd probably have to concede doing the same for Social Security COLA.
This would give Republican's cover in the sense that it's not a blatant, outright tax hike. The genius is it slowly pushes more and more American's into higher tax brackets via the lower measure for inflation. Plus few voters actually understand the concept of a chained-CPI so it's less likely to garner popular opposition.
A stellar example of why the political class must be treated like cockroaches because they act like cockroaches.