If Hillary Clinton did not have a problem, it would be necessary for the chattering classes to invent one.

Nature abhors a vacuum, journalists hate a “sure thing,” and besides, nobody wanted the Democratic nomination to be a coronation in the first place. Even so, the handwringing from Democrats that Clinton’s “sure thing” status is under threat from forces both inside and outside her camp seems at odds with the fact that she is running a very solid, effective campaign: She is leading the endorsement game by a huge margin, made a strong showing in Iowa last weekend, where she won the ringing endorsement of former senator Tom Harkin, and was reported to be “stealing the show” and “swaying doubters.”

But when you’re the frontrunner, you have nowhere to go but down. And so a dip in the polls becomes a national headline, and a narrative begins to form that Clinton could be headed for another defeat — and what’s more humiliating, a defeat that will happen for the same reasons as it did in 2008.

The Washington Post reports that the “New Hillary is hobbled by old weaknesses,” and that her campaign is exhibiting “worrisome patterns,” such as “insularity, rigidity and a sense that the operation is tone-deaf to changes happening around it.” The article continues:

Once again, worried supporters see signs of a bunker mentality in response to bad news about her email server and other controversies, and they see a candidate who can seem strangely blinkered to the threat posed by a lesser-known challenger.

Senator Bernie Sanders is drawing huge crowds with his populist message and a brazen, anti-establishment rhetoric that pundits say Clinton could never pull off. He’s built a grassroots campaign that’s riding an unlikely surge, recalling a certain other candidate who threw a wrench into Clinton’s last “sure-thing” presidential run.

The terror of Clinton’s forthcoming defeat is compounded by Dems’ predicament that her doom is the party’s too, and they live or die next November entirely on her shoulders.

“Dear Democrats: It’s too late to start over,” Chris Cilliza writes, suggesting that Democrats may be experiencing a bit of buyer’s remorse, and that whether or not they believe Hillary Clinton is the candidate they deserve, she is the one they’re stuck with. “If Democrats wanted a serious primary fight between Clinton and someone else — it’s hard to imagine who — that decision needed to have happened a year ago.”

Vice President Joe Biden might have stood a chance, but he is in no place financially to compete with Clinton, the story goes, having dithered so long that the money and talent he would need to mount a credible campaign have been siphoned off by her. Furthermore, Politico reports, the Democratic establishment would really rather the veep quietly step out of the race before he’s even entered it.

Everyone, calm down.

In the gap between press coverage of her actual campaign performance and concerns voiced about her diminishing chances lies a simple truth, which David Horsey, writing in the Los Angeles Times, put rather succinctly: “Hillary is probable, but no longer inevitable.”

Nate Silver, in a post published Monday on FiveThirtyEight, lays out how Clinton’s dip in popularity was a guaranteed thing, and that “everything that’s happened to Clinton so far in the campaign is pretty much par for the course.”

Silver observes that if weren’t for “emailgate,” there would have been another scandal; if it weren’t for Sanders, there would have been another challenger, or at least a candidate who could credibly play the challenger for a time before backing down.

Political media, he says, are guilty of “a certain type of bias: rooting for the story. Inevitability makes for a really boring story, especially when it involves a figure like Clinton who has been in public life for so long.”

“Being ‘inevitable,'” Silver writes, “doesn’t mean you’ll sweep through all 50 states with no opposition.” Furthermore, Clinton is far more “inevitable” now than she was in the 2008 election.

Clinton would rather have stronger favorability ratings than weaker ones, no email scandal, and Sanders behind her in every poll rather than all but one of them. If Joe Biden actually enters the race, I’d lower Clinton’s chances a bit; then again, I’d raise them if Biden doesn’t.

Rather, it’s that the challenges Clinton’s campaign has faced — and the media narrative about an “unexpectedly” competitive race — is exactly what you’d expect relative to the historical experience of campaigns like hers.

As one of the lowlives in David Mamet’s 1975 play American Buffalo said, “God forbid, something inevitable occurs…”

Photo: United States Democratic presidential candidate Hillary Clinton poses for a photo with a woman at the Iowa State Fair in Des Moines, Iowa, August 15, 2015. REUTERS/Joshua Lott