Here in Washington most people get that Chained CPI and other entitlement benefit cuts are measures Obama will back in exchange for Republican votes for tax increases. The Republican piece of the budget quid pro quo. Republicans put them on the table in 2011 debt limit negotiations, and have identified them in public since that time as the sorts of entitlement cuts that they'd need Obama to embrace in order consider increasing taxes.
That's less well understood outside of Washington. And now that it's an official part of his budget, Obama's muddled the ownership history. He's the one proposing it. And that's going to come as a big and unwelcome surprise to at least some voters. For them, a Social Security cut is just that -- a Social Security cut.
Now this is his budget, not congressional Dems'. They won't own Chained CPI in the same way they own the tax increases they actually voted for. But for they'll still have to answer for it.
The administration argues that Republicans might well have launched similar attacks anyhow. Obama proposed the same basic plan in sidecar negotiations with John Boehner just a couple months ago, and the differences between an official and an unofficial budget proposal are largely metaphysical. But Republicans weren't saying things like this last week. And if the gesture doesn't ultimately win him anything more than applause from elite opinion makers, this will all look like a big freebie for the GOP.