When in 2012 Trump tweeted that global warming was, in essence, a hoax (he later said that he was joking), he blamed the Chinese: “The concept of global warming was created by and for the Chinese in order to make US manufacturing non-competitive.” Conspiracies, always conspiracies, trade, always trade: when, 30 years ago, Trump was attacking the way the US paid so much towards the defence of its allies in the Far East, much of his focus was on the way that the money saved had helped build up economies that, he implied, had got too strong for America’s good. Asked in 2016 by the New York Times for his view on previous presidents, he replied that one he “really liked” was Ronald Reagan but  he had “never felt on trade we did great” in the Reagan era. 

Reagan was neither a purist nor naive (he believed in trade that was free and fair). He was not above pushing “voluntary” restraint on importers and imposing tariffs when he felt had to, but protectionism, he argued, was “almost always self-destructive”. He proposed a free trade pact with Mexico  in 1980, a forerunner of sorts for the North American Free Trade Agreement (Nafta) passed a decade and a half later. Trump recently described Nafta as “the worst trade deal maybe ever signed     anywhere”. He had opposed it even before it was approved, reportedly on the grounds that US negotiators had cut a bad deal. What Trump actually meant was that he could have handled everything so much better. 

Trump has been harping on about trade for a long time and often in a way that, reflecting his zero-sum approach to negotiation, focuses on the failure to cut a better deal. This approach slips easily into a preference for mercantilism over free trade, a choice that fits neatly under the umbrella of America First, and helped deliver the voters who had found themselves on the wrong side of globalisation, voters, particularly in the Midwest, who took Trump over the top on election day.

Trump’s victory will finish off the Transatlantic Trade and Investment Partnership with the EU, a deal already struggling even to be stillborn. The Trans-Pacific Partnership seems set for the knacker’s yard too. No new free-trade deals can be expected soon — even, I suspect with Brexit Britain. Reversing those large agreements that are already in place will be more difficult, however. Trump’s talk of imposing a 45 per cent tariff on Chinese imports if the People’s Republic doesn’t ease up on subsidies and other practices he views as unfair, would lead to higher prices in America and, eventually, slower growth, something he must understand. That 45 per cent should be seen as an opening bid in a long negotiation.

Similarly, Trump’s threat to pull the US out of Nafta (a move a president could make on his own) and impose a 35 per cent tariff on some Mexican imports risks major disruption to the supply chains of American companies, and could trigger a trade war, higher prices in the US, and, if the Mexican economy falters, a fresh surge of illegal immigration into a certain country to the north with an as yet unbuilt wall. Once again, sabre-rattling today is likely to be no more than the beginning of a negotiation that may be noisy, but will change relatively little.