As hard as it is to imagine right now, the 2012 presidential election will one day end. When it does, we will finally have a winner-and a loser. One candidate will call the other to offer congratulations; then he will stand before his supporters and publicly concede victory. As confetti falls on the newly elected leader of the free world, his former opponent will go home and begin thinking about what to do next.

Inevitably, whether for incumbent Barack Obama or his challenger, that moment of defeat will be an excruciating one. But whoever ends up having to endure it will be able to take comfort in the fact that he is joining a long tradition-a club, you might say-of hyper-ambitious individuals who share the rare experience of having been thwarted in their pursuit of the most powerful office in the land. And while it may seem like a dubious fraternity, a look back at presidential also-rans in American history reveals just how important and influential its members can end up being.

Not all failed candidates have lived down their losses gracefully, and some have found themselves stripped of whatever power they held before they tried to become president. But a surprising number have pushed past the humiliation of defeat, and laid claim to a level of prominence they might never have attained if they hadn’t run. And in some cases, they’ve changed the course of political history in ways even they couldn’t have predicted.

There have been several in-depth studies of loserdom in presidential politics, including Leslie Southwick’s encyclopedic tome, “Presidential Also-Rans and Running Mates, 1788-1996,” and a 14-part documentary series called “The Contenders” that aired on C-SPAN last year. Their overall thrust is that losing candidates have been given short shrift by historians, and that their impact on American politics has not been properly acknowledged. Most recently, in a book published last month entitled “Almost President: The Men Who Lost the Race But Changed the Nation,” Scott Farris explored some of the varied fates of major party nominees who lost in the general election. Out of their legacies emerges a kind of taxonomy of failure. There are those who were leveled by defeat and forced to fade away, those who went on to achieve great things even without the clout of the presidency, and those whose campaigns turned out to have been politically and intellectually transformative, even though they weren’t successful in the short term. Today, it seems like elections produce more well-known losing candidates than ever, thanks to primary seasons that have come to encompass months of reality-TV-style debates, and a media climate that has given the participants unprecedented exposure. In the current contest, no fewer than four Republican candidates-Rick Perry, Herman Cain, Newt Gingrich, and Mitt Romney-have been considered the front-runner at one time or another, and no matter what happens, they will emerge from the race as celebrities. Whether they win or lose, the nation will know far more about these people than we would have in previous years, and chances are we’ll be forced to pay attention to some of them for a long time.

What will become of this small army of losers, launched into a unique role in American life-and what will they come to mean to us? For answers, we have only to look back at an American shadow history: not at the presidents who won the privilege of leading the country, but at the line of disappointed people who almost did.

Whatever happens to a losing candidate’s career in the weeks, months, and years after an election, the first order of business is always the same: accepting and reacting to defeat. As it happens, the first person ever to lose a presidential election in American history, Thomas Jefferson, played it cool when he was defeated by John Adams in 1796: According to Farris, he told a friend that he hadn’t really wanted to win the presidency anyway, because he was sure “no man will ever bring out of that office the reputation which carried him into it.” Jefferson’s stoicism notwithstanding, we know that losing stings, and losing a contest that could have made you the most powerful person in the world no doubt stings uniquely hard. Hubert Humphrey called his loss to Richard Nixon in 1968 “the worst moment of ((his)) life,” and confessed he felt “so empty ((he)) could cry.” George McGovern, when he suffered the same fate four years later, joked “There are some things that are worse than losing an election. It’s hard to think what they are on Election Day.”

“It’s a crushing disappointment to lose a political race,” said Farris. He speaks from experience, having been inspired to write his book after unsuccessfully running for Congress in 1998. “Especially when you’re running for president, it’s a culmination of a career. You know you have millions of people behind you and you know you’ve let them down. And you know it’s the mark you’ll leave on history.”

The wound doesn’t heal easily: In 1984, when a recently defeated Walter Mondale asked McGovern when the pain might start to subside, McGovern reportedly replied, “I’ll let you know when I get there.” Along the same lines, the presidential historian Richard Norton Smith, who worked with C-SPAN on its documentary series, relayed a striking anecdote about Thomas Dewey, who followed his famous 1948 loss to Harry Truman with a prosperous career as the head of a New York law firm and a power broker in the Republican party. Despite the success he found after his defeat, it seems that Dewey carried the weight of the election until the end of his life. When the band hired to play at his law firm’s office Christmas party marked the boss’s arrival with a cheeky rendition of “Hail to the Chief,” Dewey was so put off that he left the celebration and didn’t come back.

But if all also-rans are initially devastated by defeat, how they respond to that disappointment is where their paths diverge. Some never reclaim the standing they once had in politics and, as Farris puts it, “exit stage left, quietly.” This is what happened to Bob Dole, who became a pitchman for Viagra and Pepsi after his 1996 loss to Bill Clinton, and to varying extents, Humphrey, McGovern, Mondale, and former Massachusetts governor Michael Dukakis. (Dukakis gave up politics entirely not long after he was beaten by George Bush in 1988, and became a college professor.)

“When you are a potential presidential candidate, you have a lot of power,” said Julian Zelizer, a political historian at Princeton University. “People are worried, naturally, that you will be the president, so they will listen to you, and they’ll do things for you.” When that possibility is extinguished, “you lose that political capital.” Perhaps even more importantly, presidential campaigns can be extremely destructive to a person’s reputation. “The only saving grace is if you win and you’re president,” said Zelizer. “But if you’re not, you just come out of it battered and bruised, and everyone knows all your flaws and all your weaknesses.”

Still, some failed candidates succeed at finding a second wind. As Al Gore put it at the end of his concession speech in 2000, “No matter how hard the loss, defeat might serve as well as victory to shape the soul and let the glory out.” Though the key word there is “might,” some failed candidates, including Gore, have indeed retained great influence, and realized major achievements, after their loss. Dewey, for instance, was a driving force behind the nominations of Dwight Eisenhower and Nixon, and remained an elder statesman within the Republican party until his death in 1971. Wendell Willkie, who lost to Franklin Delano Roosevelt in 1940, went on to write the best-selling book “One World,” which is said to have helped pave the way for the United Nations. Some failed candidates found their second acts outside of politics: James Middleton Cox, for instance, followed his 1920 loss to Warren Harding with a successful career as a newspaper publisher, while John W. Davis, who lost to Calvin Coolidge in 1924, became one of the most prominent lawyers in the country, arguing no fewer than 140 cases before the Supreme Court.

Such comebacks used to be easier to pull off than they are now. But they can still happen in our day, as evidenced by Gore, who transformed from a bearded sad sack into a Nobel Prize-winning environmentalist after the 2000 election, and even Massachusetts Senator John Kerry, whose standing on Capitol Hill-where he chairs the Senate Foreign Relations Committee-has only improved since his loss in 2004. According to Farris, Gore and Kerry-and to a lesser extent, John McCain-are examples of a new breed of presidential also-ran. “They’re trying to establish and maintain their relevance even as losers,” Farris said. “They’re trying to redefine the role of the losing candidate.”

Then there is a third category of presidential losers: those who do not necessarily go on to achieve glory themselves, but whose campaigns end up leaving a transformative political or intellectual legacy long after their headquarters go dark. Barry Goldwater, who was defeated by Lyndon Johnson in 1964, is the stand-out example of such a candidate: Though he was positively trounced in the election, the platform he promoted on the trail ended up being the foundation for the next 40 years of conservative politics. On the other side of the aisle, McGovern catalyzed a transformation in the Democratic Party by reaching out to women, minorities, gays, and young people; though their support did not get McGovern elected in 1972, those groups would become a crucial part of the Democratic Party’s base. Adlai Stevenson, meanwhile, who lost to Eisenhower in 1952 and 1956, left his mark through his eloquent rhetorical style, which influenced John F. Kennedy as an orator. (It also gave rise to the idea-still alive and well today-that the Democratic party is made up of elitist intellectuals who can’t identify with common people.)

For these candidates, there may be some comfort in knowing that although they weren’t able to become president, their efforts made a difference in the world, and perhaps even contributed to the advancement of society (or at least their party). And for a few, the march of subsequent events may even cast a kinder light on their loss, suggesting that perhaps they were just ahead of their time. As Richard Norton Smith put it, “There are candidates who look back and probably mouth the words ‘I told you so.’ That’s not to say that they spend their days, you know, pining away for what might have been. But there is that kind of satisfaction when history seems to suggest that you were on to something.”

To date, studies of failed presidential contenders have been largely limited to candidates who competed in a general election as the nominee of a major political party. Expanding the circle to include individuals who didn’t make it that far threatens to turn it into an overwhelming task, forcing us to consider a sea of wannabes and historical novelty candidates such as Harold Stassen, who ran for president 10 times between 1944 and 1988.

But as the eventual GOP nominee emerges over these next weeks and months, it’s hard to imagine that the other 2012 primary candidates we have come to know over the past year will just disappear. More likely, some of them will at least attempt to hold onto the spotlight, perhaps by following the example of former Arkansas governor Mike Huckabee, who dropped out of the Republican primary in 2008 and quickly landed his own show on the Fox News Channel.

Given such lucrative opportunities, being a failed candidate in 2012 is a very different proposition than it has been in previous years, and thanks to the extraordinary amount of media coverage there has been of the nomination process, there will be more famous also-rans than ever trying to leverage their time in the spotlight into a second-or in some cases, third or fourth-act.

“The fact is that candidates have become celebrities,” said Smith. “The president is a celebrity in chief, and the next tier down are the would-be presidents.”

It remains to be seen whether the losers who emerge from the current election end up using their platforms for real influence, or simply converting their 15 minutes of fame into speaking fees and media contracts. But to a large extent, it will be up to them to decide how lasting their impact will be. As Smith said, “The very visibility that the media generates during a campaign gives a ((candidate)) something of an afterlife. And what he does with that determines how long his shelf life is.”