“Deals are my art form. Other people paint beautifully on canvas or write wonderful poetry. I like making deals, preferably big deals.”  [Donald Trump, The Art of the Deal] If history is any guide, there is reason to hope that President Trump belatedly takes up painting this campaign season. Over the next 18 months or so, as always seems to be the case in American politics, the looming presence of a presidential election will throw up a whole host of impediments to the pursuit of optimal diplomatic agreements abroad, including with China, Afghanistan and North Korea. A brief look back at critical negotiations during the wars in Vietnam and Iraq suggests a crucial lesson: electoral politics and diplomacy do not mix …