Imagine that you are an average US Republican in early 2015. You always vote Republican, and the rest of the time you just get on with life. In 2016, you vote Republican. Sure, Donald Trump’s rants about Mexican “rapists” and his planned ban on Muslims are discomfiting, but perhaps it’s just campaign talk. Your vote turns out to be your initiation rite into a new, radical tribe.

By 2019, you are backing a president who calls white supremacists “very fine people”, who orders that migrant toddlers be held in cages separated from their parents, and tells Congresswomen of colour to go back to where they came from. Somehow you have stayed along for the ride.

Or imagine being an average Briton in 2015. You don’t particularly like Brussels, but you seldom think about it. (In polls before the referendum was called, typically less than one Briton in 10 named the EU as an important political issue.)