President Obama's months-delayed budget was finally released today, and it's being sharply criticized from both sides.

Liberals suggest the president is a "sellout" for proposing cuts to Social Security and other entitlements by using a "Chained CPI" calculation, while Republicans are falling back on their familiar "tax-and-spend liberal" attacks.
John Avlon sees this political posturing as a good sign, noting that the budget "is not a positional bargaining document, designed simply to rally the base at the outset of negotiations."

While it's possible the White House is trying to triangulate its way to a "grand bargain" on the budget, what's striking is that Obama has given Republicans exactly what they've asked for — and it's still not good enough. Republicans remain unwilling to consider additional revenues as part of any package.

In the midst of the "fiscal cliff" negotiations last year, an aide to Speaker John Boehner told Bloomberg that the GOP leader wanted to include a Chained CPI calculation even more than he wanted other entitlement cuts, such as raising the Medicare eligibility age.

Senate Minority Leader Mitch McConnell (R-Ky.) explicitly told the Wall Street Journal that if Obama offered a Chained CPI calculation for entitlement benefits, Republicans would consider finding additional revenue.

Said McConnell: "Those are the kinds of things that would get Republicans interested in new revenue."

To the annoyance of many liberals in his party, Obama included the Chained CPI in his budget.

But as Greg Sargent correctly points out, the GOP has moved the goal posts: "And so we have a moment of clarity in this debate once again: There is literally nothing that Obama can offer Republicans — not even things they themselves have asked for — that would induce them to agree to a compromise on new revenues."