Ryan, pulled to the phone from the House floor, is typically upbeat. “I believe this will turn in our favor,” he says. Ryan is all Wisconsin cheerful earnestness — the Boy Scout earning his federal budget badge. But this manner masks considerable ideological ambition. “We knew we were defining the movement,” he tells me. By setting out the case against unsustainable entitlement commitments, Ryan forced his GOP colleagues to pick a side, often against their will. The whole Republican Party will now defend and advance Ryan’s budget views — or suffer from their repudiation…

Ryan bristles at the notion that he is unraveling the social safety net. He sees it unraveling of its own accord. “The poor would be hurt worst in a debt crisis,” he says, when spending cutbacks would be sudden, drastic and indiscriminate. Reform is required to “make the safety net work, to make it sustainable.” And Ryan’s budget has taken some fire from the Tea Party right, because it rejects an arbitrary 10-year target to balance the budget — which would demand unrealistic, draconian cuts…

The real response is impossible for Ryan to make — or even, at this point, to contemplate. A budget proposal is an initial negotiating position — and increased tax revenue will be part of any final deal. Ryan’s budget already makes some revenue concessions. Currently, federal revenue stands at about 15 percent of GDP. Ryan’s 10-year plan would eventually push this figure up to an average of 18.5 percent, in line with precedent. If an eventual budget agreement were to include serious entitlement reform, I suspect that most Republicans would reluctantly accept federal revenue at 20 percent of GDP, or even 21 percent — provided these taxes were designed to minimize the drag on economic growth.