It’s a shame that Rudy Giuliani couldn’t have run for president in the fall of 2001. Back then, voters probably wouldn’t have cared if he skipped not just the Iowa and New Hampshire primaries, but all of the Super Tuesday ones, too.

Whoever the Republicans nominate—John McCain or Mitt Romney—can be counted on to stay the course in Iraq (McCain in particular), but no candidate had the gravitas that Giuliani brought to the issue of terrorism. For Giuliani had experienced something that no recent American mayor, governor, or president had—a sneak attack, shocking and deadly, in which vital decisions needed to be made quickly and for which there was no script. Giuliani’s presidential campaign was criticized for what many saw as the candidate’s overemphasis on September 11—exemplified by Joseph Biden’s memorable line that Giuliani’s every sentence consisted of “a noun, a verb, and 9/11.” Perhaps there is some truth in this, though anyone who sat through the numbing presidential debates of the last six months would know that Giuliani had a wide-ranging platform on everything from economic policy to homeland security. But he couldn’t break through his image as the Mayor of 9/11, and it is a measure of our distance from the events of that day that Giuliani came to seem a relic, a candidate whose moment had passed.

He was no relic that morning, or for years afterward. What Giuliani’s many detractors don’t even pretend to deny is that on that horrific day, his performance was breathtaking. In the heat of the moment, similarly unrehearsed, President Bush looked like a flop. He later recovered, but his fumbling first appearances, disappearance for the bulk of the day, and feeble, demoralizing speech that night made for a harsh contrast with Giuliani’s stirring presence.

Rarely in recent American history had a political leader received such a visible testing ground for the character of his leadership. Giuliani projected a profound, steely calm, and an all-encompassing competence—announcing the latest street closings or bus service changes one minute, pledging resolve and stressing American unity the next, reassuring New Yorkers all the while. He also provided Americans with a lesson in the old-school stoicism that is rapidly passing from our national life. Yet it was a stoicism that left no doubt about the suffering inside. Asked for an update on casualty figures at one point, he shook his head and said unforgettably that the losses would be “more than we can bear.”

It was in the ruins of Ground Zero, of course, that Giuliani’s presidential ambitions became plausible. His mayoral record in New York prior to September 11 more than justified a presidential run, but New York mayors, even great ones, are never considered presidential timber, barring some unique and monumental circumstance. Giuliani’s campaign difficulties have been well documented—from his moderate stands on social issues to his messy personal life, from his questionable primary strategy to his sometimes baffling passivity as a candidate. But his departure from the presidential field represents, in the end, a symbolic break from the preeminence of September 11 in our national consciousness. The psychologists tell us that we need closure—as if anything short of death ever wraps up conclusively—and one way or another, we have all long since moved on personally from that day. But Giuliani’s absence from the campaign will remove a visceral political reminder as well—a flesh-and-blood mayor who stood, covered in ash, and spoke to the nation’s greatest city on its darkest day. None of the remaining candidates can match his standard of leadership and record of accomplishment; one hopes that we choose wisely in his stead.

Perhaps Giuliani should blame Bush for his campaign’s demise. If Bush had not been so successful in preventing another domestic terrorist attack, Giuliani’s relevance to voters would be painfully obvious, and his deviations from party orthodoxy less compelling. Instead, he and Bush, the two public figures most associated with September 11, will watch from the sidelines as America turns the page.

Paul Beston is associate editor of City Journal.