In a briefing with reporters at the White House on Tuesday, senior administration officials characterized the official adoption of Chained CPI as both a recognition that rounding out a ground bargain will require making concessions to the GOP, and as a final gesture of good faith to Republicans in Congress, who've been demanding Obama propose and take ownership of entitlement cuts for years.
But the officials also stressed that Chained CPI will never become law unless Republicans respond (in unlikely fashion) by agreeing to limit tax expenditures benefiting high-income earners. If they don't, it will mark the end of Obama's two-year quest to secure trillions of dollars in deficit reduction on a bipartisan basis.
By and large the rest of Obama's budget will mirror his previous ones. But this year's blueprint also proposes financing expanded access to pre-K by increasing the tobacco tax, and a handful of other new priorities.
You can read an overview provided by the administration below.