Every time I hear that Donald Trump — all bombast, blabber and bile — is ill suited for Sunday night’s town hall debate, I recall a rare and mostly forgotten campaign moment when the former reality show star displayed empathy in an intimate setting.

The afternoon before the New Hampshire primary, Trump bowed to local custom by abandoning big arenas to participate in a town hall meeting at the Londonderry Lion’s Club. For nearly an hour, Trump Unplugged took questions from voters, speaking in a conversational tone and even, at times, feigning modesty.

[Empathy: Trump’s New Hampshire Snow Job]

The last questioner, a retired United Airlines flight attendant, spoke with audible anguish about her survivor’s guilt over her friends who had been working aboard doomed Flight 175 from Logan Airport on 9/11. As a campaign aide stood poised to yank back the woman’s microphone, Trump patiently allowed her to explain in rambling fashion how she had to quit a job she loved because she couldn’t endure the memories.

When the flight attendant finally wound down, Trump said, momentarily displaying a hidden kindly side, “I understand. Thank you, darling. I understand what you’re going through.”

Whether we will ever glimpse that Donald Trump on Sunday night remains a mystery. But in handicapping the debate, it is worth remembering that he can successfully operate in a softer, lower register.

The thrice-married Trump goes into the debate reeling from Friday’s revelation of a 2005 tape in which he bragged about groping women and trying to seduce married starlets. After initially responding with a tight-lipped press release, offering a grudging apology and taking a shot at Bill Clinton, Trump has two days to figure out how to somehow defend the indefensible.

But Trump’s sexual boasts are only one of his mounting problems. As the GOP nominee (imagine how many top Republicans have buyer’s remorse), Trump also has to figure out how to convey that he cares about governing this nation.

Trump reminds me of the old joke question about how many psychiatrists it takes to change a light bulb. The answer: “One, but the light bulb has to want to change.”

After a disastrous opening debate and facing an unforgiving electoral map, does Trump really want to change? Or has he cosseted himself in an unreality bubble filled with fake online poll numbers and fantasies about how WikiLeaks will destroy Hillary Clinton’s candidacy?

Last week’s Hofstra debate was probably the last moment for the bilious billionaire to make a remotely credible case that he had begun to take becoming the 45th president seriously. Instead, Trump tried to fake his way through a national job interview.

Maybe Trump refused to change his campaign style because he has heard too many renditions of Frank Sinatra singing, “I did it my way.” Or maybe (and I know this from the internet) Trump simply lacks the attention span and the stamina for a 90-minute debate.

In theory, voters shouldn’t need another angry eruption from Mount Donald to know that the Republicans have nominated the 2016 equivalent of witch-hunting guttersnipe Joseph McCarthy. The comparison is not hyperbolic since Roy Cohn, McCarthy’s young henchman in hate, later became Trump’s mentor.

But there is also a faction of the news media so caught up with the drama of stunning campaign reversals that all history can be forgotten in the service of a thrilling narrative. If Trump sounds remotely coherent or gets through an entire debate without insulting Rosie O’Donnell, then there will be a spate of post-debate stories about how Trump finally discovered his inner statesman.

Or, for a more outlandish scenario, imagine if Trump has been mastering the details of policy in secret.

It would be like Phil Hartman playing Ronald Reagan in the famous 1986 “Saturday Night Live” skit called “Mastermind.” At the time, in the midst of the Iran-Contra scandal, rumors were flying that Reagan was not even aware that Oliver North was running a rogue arms-for-hostages operation out of the White House basement.

On “SNL,” Hartman portrayed Reagan as the familiar amiable jellybean president in public as he chatted with a Girl Scout about her cookie sales. But once the cameras were gone, Reagan turned into an evil genius juggling all the details of the Iran-Contra scandal in his head — negotiating with the Iranians in flawless Persian and arranging complex international bank transfers in an instant.

Somehow, though, I suspect that we will not be treated to Trump the Thinker on Sunday night. Nor is the don of con likely to abandon his habit of lying, then denying.

I would not put it past Trump to claim that he is the first man in history to have won two Nobel Prizes in a single week — Peace (for not attacking Bill Clinton’s sex life) and Literature (for putting his name on the cover of “The Art of Deal.”)

Given how reluctant debate moderators Lester Holt and Elaine Quijano were to offer even the most rudimentary fact-checks, it is quite possible that it would be left to Hillary Clinton to explain that, no, Trump is not a double Nobel laureate. At which point, Trump would repeat his assertion even louder, asking voters not to believe “Crooked Hillary.” After the debate, many headlines would read: “Candidates Clash over Trump’s Nobel Prize Claims.”

I hope that moderators Martha Raddatz (who excelled at the 2012 vice presidential debate) and Anderson Cooper are made of sterner stuff. All through this year’s veep debate, Mike Pence got away with claiming that Trump had never in his life said anything more controversial than taxes should be lower.

Predicting a debate in advance remains a mug’s game. Debates can be surprising as Richard Nixon (that five o’clock shadow) and Jerry Ford (Poland is not a Communist country) learned to their dismay.

But Trump’s disadvantage Sunday night is not the town hall format, but his disdain for the office of the presidency. If he had ever read anything that wasn’t on a teleprompter or a check, Trump might recall that another man with a similar last name — Truman — said on becoming president, “I felt like the moon, the stars, and all the planets had fallen on me.”

Roll Call columnist Walter Shapiro is a veteran of Politics Daily, USA Today, Time, Newsweek and the Washington Post. His book on his con-man great-uncle was just published: “Hustling Hitler: The Jewish Vaudevillian Who Fooled the Fuhrer.” Follow him on Twitter @MrWalterShapiro.