When anger meets bigotry, the outcome could be President Trump, as Matt Frei’s campaign-trail documentary makes clear. From the hair alone you may infer the Donald. Ridiculous, unconstrained by normal rules of reason, taste and decency, and yet, against all the odds, surviving. So we must turn, with darkening eyes and heavy hearts, to the documentary by Channel 4’s Europe editor Matt Frei, which posed the question that would have seemed as ridiculous as the hair even three months ago – President Trump: Can He Really Win? Frei follows Trump on the campaign trail as the bumptious billio...