It’s the campaign event no-one is talking about, yet may provide one of the strangest, most uncomfortable nights of the 2016 US election. On Thursday night Donald Trump and Hillary Clinton will be attending the 71st Alfred E Smith dinner, an annual fundraising event organised by a Catholic charity for poor children. It’s no ordinary meal however – they’re also expected to light-heartedly roast each other.

But how? Their hatred for one another could not be clearer. Trump has called Clinton a “nasty woman” who should be in jail, and even seemed to call for her assasination. Meanwhile, Clinton has called Trump “horrific”, sexist and unfit for office.

The dinner’s organisers have called for civility. “Hillary Clinton and Donald Trump will deliver the evening’s keynote speeches in the spirit of collegiality and good-humor that has become a hallmark of the gala,” they have said. “The dinner honors a cause that transcends the polarizing political rhetoric of the day.”

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This may have worked in previous election seasons, but how it will pan out this time is anyone’s guess. How can the two candidates take part in a good-natured roast when they’re engaged in the ugliest election campaigns in American history?

In previous years, candidates have used the Alfred E Smith Dinner to made light of their opponent’s gaffes and shortcomings. In 2008, Barack Obama ribbed John McCain by making fun of how many homes he owned. “While the collapse of the housing market has been tough on every single homeowner,” he said, “we have to recognise that this crisis has been eight times harder for John McCain.”

When the US president then faced Mitt Romney in 2012, he continued to lampoon his rival’s wealth. “Earlier today, I went shopping at some stores in Midtown,” he said. “I understand Gov Romney went shopping for some stores in Midtown.”

What did Donald Trump say during the third presidential debate? Show all 9 1 /9 What did Donald Trump say during the third presidential debate? What did Donald Trump say during the third presidential debate? Mr Trump denying claims from a number of women that he sexually assaulted them “This is all fiction, all fictionalised, probably or possibly started by her and her very sleazy campaign. I didn't even apologise to my wife who is sitting right here because I didn't even do anything” Getty What did Donald Trump say during the third presidential debate? Mr Trump claiming the Russian leader had “no respect” for Mrs Clinton “She doesn't like Putin because Putin has outsmarted her every step of the way. He has no respect for her. He has no respect for our President." Getty What did Donald Trump say during the third presidential debate? Mr Trump interrupting Mrs Clinton with one of his most scathing personal attacks yet as she explained her policy on social security “Such a nasty woman” Getty What did Donald Trump say during the third presidential debate? Mr Trump claiming Mrs Clinton shouldn't have been allowed to run for presidency and that the election is rigged “She should never have been allowed to run. She’s guilty of a very very serious crime. She should not be allowed to run. And just in that respect, I say it’s rigged.” Getty What did Donald Trump say during the third presidential debate? Mr Trump voicing his “pro-life” stance during the abortion debate “Based on what she's saying ... you can take the baby and rip the baby out of the womb in the ninth month, on the final day, and that's unacceptable” Getty What did Donald Trump say during the third presidential debate? Mrs Clinton suggesting this is not the first time Mr Trump has claimed results against him have been rigged “There was even a time when Trump didn't get an Emmy for his TV programme three years in a row and he started tweeting that the Emmys were rigged” Getty What did Donald Trump say during the third presidential debate? Mrs Clinton responding to Mr Trump's lewd comments about women “Donald thinks belittling women makes him bigger. He goes after their dignity and self-worth” Getty What did Donald Trump say during the third presidential debate? Mrs Clinton implying Mr Trump is a “puppet” of Russian president Vladimir Putin “He'd rather have a puppet as president of the United States” Getty What did Donald Trump say during the third presidential debate? Mrs Clinton comparing her political experience to Mr Trump's former television role “On the day I was in the situation room monitoring the raid that brought Osama Bin Laden to justice he was hosting the Celebrity Apprentice” Getty

Presidential candidates have always attacked each other and swung below the belt, yet this year the political climate seems to have swung into a place unprecedented in its toxicity. Among a long list of wild accusations – including that the election will be “rigged” – Trump has called Clinton the “devil”, and brushed off sexually assault claims by accusing her husband Bill of rape.

It’s hard to see how the candidates could ever see eye to eye again, and embrace the ethos of the Alfred E Smith dinner. McCain accused Obama of “palling around with terrorists” during the 2008 campaign, yet both men were able to come together in a show of unity at the event.

“I am especially honoured to be here tonight with my distinguished opponent Senator John McCain,” Obama said at the time. “It is a tribute to American democracy that the two of us could come together and sit down at the same dinner table without preconditions.” (A running theme of McCain’s campaign was that Obama was naively willing to meet Iranian leaders without preconditions.)

There is a chance that Trump and Clinton may grit their teeth and get on with it, delivering genial and tightly scripted speeches. But Trump cannot stay on script, and doesn’t seem to have an even vaguely acceptable sense of humour. He once decided it was funny to mock a disabled reporter.