In 20 seconds on Saturday Donald Trump appeared to tear up Article 5 of the Nato charter, the single most important document in the architecture of global statecraft for the past 75 years. In a few hours yesterday senior senators in the Republican party he now dominates said, in effect, it was nothing to be worried about; he was simply upping the ante in a long-running and important debate about who pays for Europe’s defence. Trump, ad-libbing, told a rally in South Carolina that as president he would not only not order US forces to protect a fellow Nato member if it was “delinquent” on defence payments; he would encourage Russia to “do whatever the hell they want”. Article 5 requires members to regard an attack on one as an attack on all, and to come to each other's defence. Jens Stoltenberg, the Nato secretary general, said the mere suggestion the clause would not be honoured “undermines all our security, including that of the US”. The White House and the Republicans' dwindling corps of never-Trumpers denounced the remark. But Senators Lindsay Graham and Marco Rubio, said, respectively, “Give me a break – I mean, it’s Trump,” and “I have zero concern”. Cue sleepless nights in Lithuania, and perhaps precisely the military build-up Europe needs.