Ross Douthat builds on my “GOP’s Vietnam” article and comes in for some flak from Kevin Drum, among others. Drum is right that Bush’s domestic agenda would have faced resistance, war or no war, but he misses the bigger picture of how the Iraq debacle has affected the GOP.

First, as Ross notes, the war re-energized the activist left. Howard Dean may have lost the Democratic nomination in 2003/4, but the “netroots” that grew from that campaign and from other forms of antiwar, anti-Bush activism became very important very quickly. There’s no doubt they contributed to Democratic congressional successes in 2006.

The war also played a role in getting veterans and even former Republicans, such as Jim Webb, to run for office as Democrats in ’06. These were not only strong candidates in their own right, they were candidates who helped dispel the notion of Democrats as uncomfortable with the military. (You might have thought the nomination of Vietnam combat veteran John Kerry in 2004 would have accomplished that, but for reasons I’ll discuss separately, it didn’t.)

By 2007, opposition to the war was widespread enough to fuel an insurgency within the Republican Party itself. Going into the 2007/8 GOP presidential debates, no one would have picked the septuagenarian Rep. Ron Paul as a figure likely to build a mass movement—he seemed less well-positioned to do so than, say, anti-immigration leader Rep. Tom Tancredo or perhaps even Rep. Duncan Hunter. But Paul’s showdown with Rudy Giuliani over foreign policy in the South Carolina debate galvanized a new force in GOP politics.

That new force, of course, has special appeal on America’s campuses and among Republicans under 40. Several key congressional figures, including Sen. Rand Paul and Rep. Justin Amash, have arisen directly from or benefited from connection with this new force. It’s not just about foreign policy, but that was the spark at its moment of conception, so to speak. The fact that something like this exists on the right suggests just how thorough the country’s disillusionment with Bush-era foreign policy has been.

The economic crash by itself would have doomed Republicans in 2008—at least it would probably have doomed the presidential nominee. But absent the crash, the war had already eroded the Republican brand considerably and was going to be a drag on GOP prospects in 2008 and 2012 whatever the state of the economy.

Those are short-term and fairly concrete consequences the war has had in domestic politics. (The “war” being not just Iraq but the “War on Terror”—of Iraq was the burning example.) My magazine essay attempts to tease out some longer-term implications.

The question the essay was intended to answer was this: how can foreign policy have any effect on domestic politics when it’s well known that Americans do not rank the issue very high on practically any opinion survey? The facts of the past decade do seem to suggest that botched wars are leading indicators of a party’s decline—as outlined above, it was obvious that something was wrong with the GOP brand well before the financial crisis hit. But how could that be?

The answer, I argue, is that foreign policy is not just about foreign policy, it’s also about religion, sex, fears of radicalism, shame, and any number of other psychological qualities that can be addressed under the rubric of “culture.” Vietnam seemed to provide one example of how these things could influence one another. (The aftermath of World War I might be another, but that was something I only touched on lightly given my space constraints.)

Each example is messy: the Vietnam era was also the civil rights era, and there likely would have been political upheavals even without the war. The Iraq era runs into the Great Recession, which again would have been sufficient to shake up our politics. But in each case, one can see how the war in question intensified and helped to polarize the disruptions of the time. The migration of neoconservatives and “Reagan Democrats” away from the Democratic Party owed a great deal to the way the Vietnam War affected the party, and the merging of antiwar radicalism with “black radicalism” was part of what drove the neocons to defect when they had earlier been supporters of the civil rights movement. Radicalization might still have taken place without the war—though that’s hard to say with much confidence—but as it happened, the war clearly pushed things further than they otherwise would have gone.

The effect of Iraq on the GOP hasn’t been as dramatic, but the outlines look similar. An intelligentsia—realists, in this case—has been migrating away from the party. An insurgency to redefine the party’s identity has arisen in the form of Ron Paul’s movement. And young people, who have tended to be relatively more pro-war in the Vietnam and Iraq era alike, have nonetheless had their impressions of the GOP colored unfavorably by the Iraq War. As I argue in the magazine, these are not isolated developments but indicate two things that pose a deadly danger to the GOP in future national elections. First, the politics of the Vietnam era, with all the advantages it conferred on the GOP in foreign policy and domestic cultural politics, is now well and truly past. And second, the wars of today have contributed to shaping a new image of the Democratic Party in contrast to the Republicans, as the party of relative restraint and competence. Drum is right that in many respects Obama’s foreign policy resembles Bush’s—as Nixon’s resembled LBJ’s—but there’s something about starting a war you can’t finish that really seems to cost a party in the eyes of a public.