JD Vance is trying hard not to be weird - and it’s making him seem more menacing still | Emma Brockes

The overriding and at times darkly comic impression, watching JD Vance's exchange with Tim Walz in the vice-presidential debate on Tuesday night, was that Vance's top-line imperative was to demonstrate to America just how extravagantly not-weird he is. Nothing to see here! Just a guy with a placid expression, nice manners, a noble desire to find "common sense, bipartisan solutions", and a lovely little quiff. His affect was so relaxed, so urbane, that at points during the debate he could have been twirling a cane and slinking around a corner like Top Cat.

And while the event itself is unlikely to move the election needle, the performance of the two contenders for vice-president was a useful measure of where each campaign thinks its weaknesses lie. Both men were required to perform sincerity, a tough call in such a rehearsed and high-pressure setting, but only Vance was tasked with having to perform normality - which he did, up to a point. Walz, meanwhile, had to struggle to back up his charm with something steelier and more purposeful than relatability. Whereas a candidate for president can be all flamboyance and jazz hands, it is the role of the vice-president to be a sober voice in the room - and for 90 minutes, both men tried to out-grownup each other.

The result was, to some extent, a gratifyingly low-drama exchange in which each man was lavishly courteous to the other. When Walz mentioned his son had witnessed a shooting at a community centre, Vance absolutely nailed a tone he customarily struggles with - being recognisably human - and immediately offered his sympathy. Walz, meanwhile, was conciliatory on the subject of how to prevent another school shooting and allowed that his opponent was, at least in principle, broadly against the murder of small children. For Walz, however, the debate was a harder proposition from the get-go, given just how low the expectations were for his rival.

And in the first instance Walz did seem to fluff things. He is, he has said, not a natural debater, happier charming voters while buying a doughnut or holding a cat than facing someone on stage. Vance, by contrast, is absolutely the champion debater you remember from college, right down to his dead shark little eyes and his resting smug face. (Walz's resting face ranged from gimme-a-break incredulity to full blown oh-god-we're-all-going-to-die fright eyes, and by the end of the debate, the corners of his mouth drooped so heavily he looked like Marlon Brando in The Godfather.)

Given the biases we bring to the party at this stage, I tried, for the sake of argument, to allow for the possibility that Vance's reasonable air connotes a reasonable outlook and to see Walz's under-energised performance through the eyes of those sympathetic to Trump. Maybe Walz's folksy charm is a smokescreen for something more mercenary? Maybe Vance isn't as bad as he has seemed until now? But then he got going on how restricting abortion is a way of "giving women more options" and I thought: "You creepy little putz," and was back to square one.

This is the crux of the matter with politicians such as Vance, whose job it is to put a civilised face on Trumpist extremism. In calm, measured tones he defended creating the conditions in which, denied adequate healthcare in their locality, miscarrying women die while travelling across state lines. Pleasantly, he suggested that school shootings in the US might be countered by making the "doors" and "windows" of schools "stronger". He argued that the real victims of the US immigration crisis are the border patrol agents "who just want to be empowered to do their job".

And when Walz asked him point blank if he believed Trump lost the 2020 election, he dodged the question entirely. "I'm pretty shocked," Walz said, and he looked it. There is something arguably weirder about presenting fanatical, life-endangering positions in the urbane tones of someone offering us all a great deal, and yet, at times during the debate, the more superficial oddness of Vance was still visible. I laughed out loud when he described Usha, his wife, as a "beautiful woman who's an incredible mother to our three beautiful kids and also a very, very brilliant corporate litigator". The bottom line? Vance really is creepy.

He is also, of course, dangerous. There was a single, fleeting moment when I thought Vance dropped his mask, and that was 30 minutes in, when Walz mentioned Springfield, Ohio, in reference to Vance's lie about Haitian immigrants eating pets. Walz, playing the more-gracious-than-thou game, allowed that Senator Vance is genuinely interested in solving the immigration problem, but that, "by standing with Donald Trump" he was only making it worse. It was as close to accusing the man of stark, self-interested, near-psychopathic venality as the tone of the exchange would allow. A flash of anger crossed Vance's face before the banality of his demeanour returned.