Yglesias says, correctly, that the only way we’ll get any budget deal now — or, I’d say, any time in the next several years — will be if conservatives come up with an offer. And they won’t.

The key point is that conservatives are insisting that no tax be raised on anyone — yet they have not been willing to embrace the only policies that could balance the budget given that insistence, namely very large cuts in defense, Medicare, and Social Security.

Think of its this way: over the 2001-2007 business cycle, the United States ran persistent deficits; so revenue wasn’t enough to cover expenses even then. In the future, even if we manage to limit cost growth in Medicare, the aging of the population will raise costs by several percent of GDP. If no revenue can be added from any source, that means that there must be huge cuts in the big-ticket items.

But what Republicans want is for Obama to propose those cuts– and therefore to take the political heat — while they give up nothing whatsoever.

Not going to happen.