“Will you shut up, man?” As insults go, it’s not exactly a classic. But Joe Biden’s exasperated sigh towards Donald Trump in that not-so-super Tuesday debate was refreshing in its unlettered honesty. And it may yet prove to have some wider significance.

We have all longed to mutter the same to a prattling, self-serving bore, or a clownish, attention-seeking tweenage bully. In an otherwise stilted and fumbling performance, Biden’s off-the-cuff retort felt exciting, at least — a sign of something promising in the Democrats’ aged retainer. Defiance? Vim and/or vigour? Life in the old dog yet? We’ll see. But it could just be that it summed up how many almost-unemployed, fence-sitting, politician-doubting, covid-fatigued middle Americans feel at this moment — and that will count for something.

After all, presidential campaigns so often hinge on these tiny, off-hand, unpredictable moments in the thick of the fight. Here are a few of the more pivotal (and colourful) moments in American presidential debate history.