The most remarkable thing about Monday’s foreign-policy debate in Boca Raton was how unremarkable Mitt Romney was. That’s a compliment. For an hour and a half, Romney played to the American middle, courted the mainstream. More or less agreeing with every substantive position of President Obama’s, Romney tried to find small differences that would make him appear more cool, more reasonable, and more Presidential than the President himself. Romney made no calls to invade this country or that one, no messianic invocations of America’s mission in the world. He came off as calm and pragmatic, even boring, and unbound by the straitjacket of any ideology.

No big deal, right? Not unless you place the foreign policy Romney outlined Monday night against the extreme vision he has put forth in his domestic agenda. At home, in the areas of tax policy and the role of government, Romney (and Paul Ryan) would take America to places it hasn’t been since early in the last century. Many of the assumptions that underpin Romney’s fiscal and economic policies, like the idea that tax cuts will spur economic growth, are unsupported by empirical evidence.

All of this raises an intriguing question: Why has Romney become cool-headed and middling abroad while remaining far-out and irrational at home? Why the different learning curves?

Let’s recall the foreign policy that Romney outlined in Boca Raton, if only because it departed from much of what he’d been saying before he got there. With the whole nation watching, Romney spoke coolly about Iran, saying he would use military force to stop that country from developing a nuclear weapon only as a last resort. He declared that he would refrain from using force to oust the murderous regime in Syria, which makes him at one with President Obama. Romney endorsed the President’s plan to withdraw American troops from Afghanistan by the end of 2014. One of the few differences arose over Iraq; Romney chastised the President for failing to leave a residual force behind in Iraq—a fair criticism, especially as that country teeters toward civil war.

Whence the moderation? Until recently, of course, Governor Romney, and the G.O.P. more generally, could hardly find a problem they didn’t want to drop a bomb on. Indeed, ever since the beginning of the Cold War in the late nineteen-forties, the Republican Party could claim, with some justification, that it was more aggressive in defending American principles abroad. What changed was the war in Iraq, launched on cherry-picked intelligence and waged, at least in its early years, with a nearly blind incompetence. The war cost a trillion American dollars and nearly forty-five hundred American lives. A Republican President, with broad support, launched the war in Afghanistan as well, and then steered it in a disastrously wrong way. We haven’t seen the end of that one yet, not by a long shot. But America is exhausted. Romney said as much last night: “We don’t want another Iraq. We don’t want another Afghanistan.” Given the moderation Romney put on display last night, I think it’s safe to say that the Republican Party, or at least some of its leaders, learned something from its experience over the past decade.

What, then, of Romney’s domestic agenda? The other catastrophe of the Bush Presidency was the financial meltdown of 2008. The overwhelming weight of the evidence suggest that the financial crisis was a direct consequence of three decades of ideologically motivated legislative and regulatory change, spearheaded by conservative elected officials and paid for by their wealthy benefactors. (Democrats supported and even led the enactment of much of this agenda, of course.) Given that evidence—the unshackling of banks, the neutering of regulatory bodies like the Securities and Exchange Commission, the devastating effects of Bush’s tax cuts on the nation’s finances—you might think the G.O.P. had learned something from the financial crisis, as it did from Iraq. It hasn’t. When it comes to Ayn Rand and Arthur Laffer, the Republicans are doubling down.

Why the difference? It’s impossible to say for sure. Bad ideas have a way of clinging to the brain, even in the face of overwhelming evidence. One possibility: the Republicans haven’t really paid a political price for their errors—at least one commensurate with their mistakes. President Obama won in 2008, but not in a landslide—and, as the Democrats well know, it’s only a landslide that forces politicians to rethink. The economic hole Obama inherited was so vast that he may well lose next month, an outcome that would sustain the G.O.P.’s ideological agenda for years to come—or at least until the next reckoning. Maybe then, and only then, would the learning curve begin to turn.

Read “Atonement,” Dexter Filkins’s piece in the current issue about an Iraq vet’s redemption. And see our full coverage of the Presidential debates.

Photograph by Marc Serota/Getty.