That’s because budget deals simply don’t last very long. Think of the last extended series of deficit fights, which emerged after Ronald Reagan proposed and Congress passed tax cuts in 1981 — and the various efforts, beginning in 1982, to do something about the resulting enormous deficits. After several failures (such as the Gramm-Rudman-Hollings procedure while Reagan was still in office), the deficits were finally dealt with, first by a grand bargain when George H.W. Bush was president and then a partisan plan passed by Democrats when Bill Clinton was in the White House. And yet, those accomplishments of the early 1990s were entirely erased by Republican budget policies during George W. Bush’s presidency.
I suppose it might comfort George H.W. Bush a little bit to know that budget analysts consider the deal he signed off on to have been quite successful in lowering the deficit. (Or, perhaps, not.) But I suppose if “legacy” is about reputation among historians, Bush might wind up receiving credit for it, and Clinton for his 1993 budget. However, if legacy is about long-lasting policy achievements, then both Bush and Clinton have basically nothing to show for their efforts. The truth inherent in budget politics is that whatever is done today can be undone tomorrow. Set up an entitlement that works and it will likely last. But tax increases and spending cuts can almost always be reversed.
Again, that doesn’t mean that there are no legitimate reasons for Obama to prefer a grand bargain. But presidents worrying about their legacies is always a sign of trouble, and thinking about budget deals in terms of a “legacy” is just plain silly.