The candidacy of presumptive Republican presidential nominee Donald Trump—whether it is ultimately successful or not—is going to have a huge impact on the global markets over the course of the summer, London-based financial journalist Matthew Lynn writes in an opinion piece for MarketWatch. The greatest impact may well be outside the United States, as American presidents often have surprisingly little ability to control domestic policy, especially when they don’t control Congress. But they have huge power over foreign policy, whether it is political or economic. Read the original piece from MarketWatch.