BLAME WHERE IT BELONGS. I think I'm a little more sympathetic to the overall premise of Matt's argument than Ezra, although to me it's not so much about the war (arguably the greatest period of progressive policy-making in American history, after all, happened during the escalation of the Vietnam war) as a straightforward story about how American political institutions make major progressive reform very difficult under all but the most fortuitous circumstances.
I must admit, however, intense annoyance about Matt's claim that Al Gore is to blame for "squander[ing] the opportunity" presented in 2000. First of all, we don't know what kind of reform Gore might have been able to attain, especially a Gore elected to a second term (FDR didn't exactly run as a fire-breathing progressive in 1932.) Given that the election was "lost" in relatively conservative swing states, there were good strategic reasons for not running further left, but this doesn't tell us exactly what his policy agenda would have been. But, also, I don't like going along with implications that the 2000 election was entirely about Gore's weaknesses as a candidate. Gore didn't design the definitively irrational system the Constitution uses to select presidents. He didn't insist on Ralph Nader's vanity campaign. He didn't encourage the Florida state legislature to create its election statutes by having the attorney general's infant son scrawl something in crayon. He didn't appoint 5 partisan hacks to the Supreme Court. He didn't force outlets like the Washington Post and the New York Times to conduct an endless smear campaign against him, or generally cover this highly consequential election like an elementary school student council race. (And lest you think that the appalling media coverage is just sour grapes about an inherently awful candidate, I would note, for example, that a majority of people who actually watched the first Bush/Gore debate thought the latter had won -- but people who got their information through press coverage of the debate didn't.)
I don't recall Gore underestimating the importance of the 2000 campaign, but I do recall lots of alleged liberals -- represented for me by Frank Rich -- who claimed that the election didn't really matter and that Bush and Gore were indistinguishable (which also relied on assumptions that Bush was a harmless moderate, something that was plausible as long as you ignored his record as a governor, his supporters, and his platform.) I don't claim that Gore was a great candidate. But when it comes to squandered opportunities, I'm a lot more upset at the media and the idiot "Gush-Bore" crowd than I am about someone who ran a serious campaign and would have been a good president.