House Budget Committee Chairman Paul Ryan, R-Wis., gives the GOP response to President Obama's budget submission for Fiscal Year 2012, on Capitol Hill in Washington, Monday, Feb. 14, 2011. (AP Photo/J. Scott Applewhite) (J. Scott Applewhite/Associated Press)

But the answer to that dilemma is also plain, as the Concord Coalition acknowledges. The president’s budget has to be specific. Ryan’s can be vague:

Unlike the President’s Budget — which lists policy proposals and numerical targets for revenues, deficits and spending — the congressional budget resolution only requires numerical targets, and normally does not go into the specific policy proposals to achieve them. This will allow a degree of vagueness that will make it easier to tout bottom-line numbers without necessarily having to fight over every small proposal to achieve them.

What are his other options? If he can’t allow taxes to increase, that adds $5.6 trillion to the deficit over and above CBO’s current projections, as they assume the Bush tax cuts and a variety of other cuts will expire. If he's using the CBO’s economic projections, those are quite pessimistic and do not allow us to assume we’ll just grow our way out of the hole. If his deficit reduction doesn’t kick in for decades, as is true in his Roadmap, then his budget will look worse than the administration’s and his reputation as a fiscal hawk will be trashed. But if he tries to sharply cut spending popular among the middle class or seniors, he may lose his party the next election.

It’s not an easy set of choices. But it’s clear that the easiest answer is to simply pick some improbably low target for spending and not say how we’ll make the cuts and choices necessary to get there. Which is, of course, no answer at all.