America loves an underdog. Donald Trump hates losers. Now that the self-described billionaire and Republican nominee for president is tanking in the polls, he risks missing the opportunity offered by the former and may end up turning into the latter. And campaign observers and behavioral experts say it's due to his own campaign trail behavior.

For another candidate, a slide in the polls would be surmountable, and might even end up working to his or her advantage when the candidate uses it to show gumption and vulnerability. Sen. John McCain, for example, was trailing in the 2008 Republican presidential primary polls, and left for political dead by the press. He learned, re-grouped and became the nominee.

The late Sen. Edward M. Kennedy, D-Mass., found himself in a stunningly close race against Republican Mitt Romney in 1994, stepped up his campaign game and was able to recast himself as a fighter, winning re-election. Bill Clinton declared himself "the comeback kid" after placing second in the New Hampshire Democratic presidential primary, branding him as an underdog even as he went on to thrash his opponents. Hillary Clinton, labeled a front-runner in 2007, lost the Iowa caucuses and was behind in polls in New Hampshire. She teared up at a campaign event in a rare show of emotion and public frustration – and ended up winning the Granite State primary.

But Trump is no ordinary candidate, analysts note. Far from casting himself as the Horatio Alger of either the business or the political world, Trump has incessantly referred to himself as a winner, and to critical media and his foes in the press as "losers" or "failing." He has bragged about his proclaimed wealth, about his business empire, about the women he has allegedly dated in the past and even, at a presidential primary debate, about his sexual prowess. So he puts himself in an awkward position, asking supporters to cheer someone who – for the time being, anyway – is losing.

"His trajectory was determined by the winner image. It had to be, because of [the campaign slogan] 'Make America Great Again,' and comments that 'we don't win anymore.' He has got to be the vessel for winning," says Peter Fenn, a veteran Democratic consultant. "And if he's a vessel for losing, it's not much of a vessel."

Trump has in the last week made remarks that suggest he is considering the possibility he could lose to Democratic nominee Hillary Clinton. "If at the end of 90 days I fall short because I'm somewhat politically [incorrect] even though I'm supposed to be the smart one and even though I'm supposed to have a lot of good ideas, it's OK. You know, I go back to a very good way of life," Trump told CNBC Thursday. In another part of the interview, he said, "at the end, it's either going to work, or I'm going to, you know, I'm going to have a very, very nice, long vacation." As recently as May, Trump told Fox News' Megyn Kelly that "If I don't go all the way, and if I don't win, I will consider it to be a total and complete waste of time, energy and money."

Trump also remarked recently that he is having trouble in red-state Utah – a startling admission for a man who has insisted, for example, that he is "doing very well with Latinos" despite numerous polls showing Trump drawing less than 25 percent of Hispanic voters. And on his Twitter account – generally dominated by slams against Clinton and the "dishonest" media – Trump has started thanking lawmakers who offered their endorsements, an unusual recognition that he might need others' help to get the job he proclaimed at the Republican National Convention only he could do.

But Trump's problem, says University of South Florida professor Joe Vandello, is that he is not the "lovable loser" or come-from-behind hero Americans love to see succeed in sports and in politics. Olympics watchers cheer for the refugee athletes, no matter where they are from, but there was no sympathy for underdog South African swimmer Chad LeClos, who taunted champion Michael Phelps before their competition.

Far from being chastened by his drop in support, Trump has gone on the offense, accusing President Barack Obama of being the "founder" of the Islamic State group and obliquely suggesting Clinton might be assassinated by "Second Amendment people." That has establishment Republicans worried that Trump will lose and take GOP senators and congressmen with him.

"If you see that you're losing, you generally accept the humility that comes with losing," says Matt Mackowiak, a Republican consultant. But "we're not seeing a lot of introspection and humility from Trump right now," he adds.

"Virtually every candidate tries to position themselves as the underdog. You won't find that with Trump. It's not his thing; he's all about being a winner," agrees Vandello, who has done extensive research on the psychology behind support of underdogs in athletic and politics.

"His whole persona is about being the tough guy, being the boss. He literally lives in a gold palace in the sky," Vandello adds. "Even if he is objectively an underdog, given his position in the polls, I think he would have a hard time selling that image."

Candidates have recovered from dips in the polls before, and Trump certainly could bounce back. But that generally happens when the candidate has learned something from the struggle and adapted his campaign to fix the problem. And Trump, Machowiak fears, may just have decided he doesn't really want the job. Machowiak is not a Trump supporter but worries incumbent GOP lawmakers could lose their races because of depressed Republican turnout. Senate Majority Leader Mitch McConnell, R-Ky., is concerned, too, telling a Louisville civic group this week that the GOP's chances of keeping Senate control are "very dicey."