Obama would not be president today if it weren’t for the Iraq War. Hillary Clinton’s inability to explain her vote for the invasion — and Obama’s well-known speech against it — were what enabled a political unknown with little experience to snatch the nomination from a seemingly unbeatable national figure who had actually lived in the White House. Obama’s rise came at a time when Democrats were deeply divided over how aggressively to confront the Bush administation over the Iraq debacle. His victory in the primary represented the triumph of the party’s antiwar wing — which supposedly had been responsible for Dem weakness on national security issues for decades — and a defeat for the “hawkish” wing of the party that insisted the best way to be seen as “tough” on national security was to cede the argument over it to Republicans.

The argument both Hillary and McCain made against Obama was that he was too green and naive to handle seasoned world leaders and foreign policy crises.

How odd it is, then, that Obama’s announcement today that all U.S. forces will return from Iraq by the end of the year looks like the latest in a series of national security victories that have essentially wiped away the GOP’s advantage on the issue?

A lot of debate is centering today on whether the announcement will or won’t help Obama in the 2012 election. Ben Smith gets it right on this point, I think, arguing that it may contribute to generally positive impressions of his character and steadfastness, though the economy is ultimately going to loom largest. But beyond Obama’s reelection, it’s worth asking whether Obama’s string of victories on foreign policy will have a more far reaching effect by putting an end to the GOP’s dominance on the issue for a long time.

Putting aside the entirely legitimate liberal criticism of Obama’s prosecution of the war on terror, his penchant for secrecy and his disappointing civil liberties record, the Obama administration got Bin Laden, decimated Al Qaeda, and helped set in motion the fall of Gaddafi. He has done this while taking steps to improve relations with the broader Muslim world and, now, while essentially ending the Iraq War, which once was the most polarizing issue in this country. His outreach to the Muslim world and initial opposition to the Iraq War once got him branded as weak, but in light of his larger record anyone pointing to these things as signs of softness on national security will come across as hollow, spiteful, and unpersuasive.

In other words, Obama has completely scrambled the traditional calculus. GOP criticism of Obama’s policy on Libya — and Mitt Romney’s criticism of Obama’s announcement today — sounds confused and incoherent. The neocons seem to have lost their grip on Republican candidates and officials, with many of them now veering between ill-defined isolationism and a desire to avoid foreign policy completely. The GOP seems rudderless on the issue. Obama gets consistently high marks on his handling of terrorism — and his success on that front has already enabled his campaign to go on offense against Republicans.

Foreign policy, of course, has receded in the minds of voters because of the economy. When the focus returns to foreign policy and national security we’ll have a clearer sense of just how much Obama has changed the landscape on these issues. But it’s worth appreciating how unlikely it seemed only a few years ago that he, of all politicians, would be the one to shift it to the degree he did so far.