It is sometimes hard to remember just how radically conditions have changed in a few short years. Back in the summer of 2004, as the nation prepared for its first major-party political conventions since the Sept. 11 massacres, a good deal of the pre-game chatter, both in the press and among the conventioneers, was about whether the tens of thousands of sitting-duck politicians, staffers, and journalists would be the target of a new and insidious terrorist attack.

Going through security was a sweaty, nerve-jangling exercise in questioned mortality. Random loud noises from inside the convention center were treated with maximum suspicion. And when the Republican Party convened in New York City, just one week shy of the three-year anniversary of that awful day in lower Manhattan, the intentional symbolism was leveraged with maximum effect to portray opposition Democrats as appeasing, Euro-loving "girlie-men" unable to recognize the grand American throughline from fighting Hitler, to fighting communism, to fighting the War in Iraq.

"You know, we're just not going to let the terrorists determine where we have political conventions," said former New York Mayor and then-2008 hopeful Rudy Giuliani, in an uproarious opening-night speech. Democratic turncoat Sen. Zell Miller brought the natives' blood to boil by fetishizing domestic political unity in times of war and thundering that "it is the soldier, not the reporter, who has given us the freedom of the press." And Arizona Sen. John McCain, after three-plus years of tangling with the president and building his own independent fanbase, wrapped his long-reluctant arms around George W. Bush "and the steady, experienced, public-spirited man who serves as our Vice-President, Dick Cheney," declaring that "only the most deluded of us could doubt the necessity of this war."

Four years later, McCain is the nominee of his party precisely because of those "deluded" anti-war voters, who came out for him in the GOP primaries in numbers far outpacing even Ron Paul, thus making up for the fact that the maverick never won a plurality of self-described Republican voters in any early-primary state. The ongoing, fundamental challenge to McCain—which is producing a fundamental schizophrenia in his campaign—is to keep his party's restive base disciplined and enthusiastic, while maintaining his crossover appeal to independent and centrist-Democrat voters, who largely hate the war and hate neoconservative foreign policy.

Ever since wrapping up the Republican nomination, McCain has fallen all over himself insisting that he's a moderate "Eisenhower Republican" on foreign policy, and not a radical interventionist. That is, until an international crisis softens the ground of public opinion for some trademark exaggerated bellicosity.

But political conventions are different, especially those attempting to knit back together a fraying coalition already beginning to express doubts about the foreign policy credentials of vice presidential pick Gov. Sarah Palin of Alaska. Nothing unites Republicans—or highlights the substantial differences between McCain and Sen. Barack Obama (D-Ill.)—than a stern pounding on the Democrats' limp-wristed internationalism. But with the whole country watching on television, such a message could drive away the voters McCain can't win without.

The 2008 McCain has tried to assuage weary skeptics, both domestic and foreign, that "when we believe international action is necessary, whether military, economic, or diplomatic, we will try to persuade our friends that we are right. But we, in return, must be willing to be persuaded by them." But the 2004 convention McCain (consistent with his entire adult career) sang a much different tune: "As we've been a good friend to other countries in moments of shared perils, so we have good reason to expect their solidarity with us in this struggle....even if we have, at times, been disappointed with the reactions of some."

The 2008 McCain says the wisdom of the decision to invade Iraq is "a job for the historians," but the 2004 convention McCain was both more certain and less in a mood to hear otherwise: "It was between war and a graver threat. Don't let anyone tell you otherwise. Not our critics abroad. Not our political opponents. And certainly not a disingenuous film maker."

Will a McCain-led Republican Party once again try to re-punch their ticket to the White House by thundering against the foreign policy of Michael Moore? It feels like the American context has changed too much since then. But old campaign habits die hard.

And, most importantly, even if McCain finds some magical formula (realistic idealism!) to bridge his political gap, the candidate's core convictions on foreign policy center around a principled interventionism that far outpaces anything ever envisioned by George W. Bush. The Republican Party platform might put McCain's foreign policy best: "In dealing with present conflicts and future crises, our next president must preserve all options. It would be presumptuous to specify them in advance and foolhardy to rule out any action deemed necessary for our security."

Matt Welch is the editor in chief of reason and the author of McCain: The Myth of a Maverick.