I'm a little unconvinced by Matt's pessimism here, though I think it's much more of a wait-and-see situation than anything you can actually argue out. I'm skeptical that we're going to see any major progressive reforms in the very near future, but I think we're going to see quite a bit of momentum gathering behind such reforms in the very, very near future, so who knows. Troubles abroad, however, only make organizing at home more likely. If a Democratic president has to spend much of his time doing the unpleasant, uninspiring work of extricating our armies, he's more, not less, likely to try and craft inspirational proposals at home. Indeed, I'd be surprised if the arguments weren't explicitly linked, along the lines of, "it's time to stop building firehouses in Baghdad and start building them in Baltimore!"
Also, Matt says that, "Besides the New Deal, the other major era of progressive change in recent American history was the booming postwar years, the same period during which the vast welfare states of Western Europe were created." I'm not sure what he means by this. As Chris Howard explains in The Welfare State Nobody Knows, progressive policy achievements have actually been much more steadily achieved than most folks realize. You have the New Deal, of course. But in the 40s and 50s, you have the GI Bill, subsidized school lunches, disability insurance, Perkins loans, and the mortgage and health care deductions (both middle class tax entitlements). The 60s are the Great Society, with Medicare, Medicaid, welfare, Head Start, and so on. The 70s see the introduction of Supplemental Security Income, Section 8 housing, and the Earned Income Tax Credit. The 80s hugely reduced the tax burden on the poor through the 86 reforms. The 90s give us SCHIP, the Americans With Disabilities Act, a huge expansion of the EITC, and the creation of the Family and Medical Leave Act. And even under Bush, the 2000-2006 has seen No Child Left Behind (remember: it was, in many ways, a Ted Kennedy and George Miller priority) and Medicare Part D. It's simply not the case that progressive policy making has stalled except for two short periods during the century.