The Globe and Mail reports in its Wednesday edition that Donald Trump's latest tariff tantrum was a sucker punch to Prime Minister Mark Carney. Guest columnists Fen Osler Hampson and Tim Sargent write that the new measures impose 50-per-cent duties on $20-billion (U.S.) worth of Canadian goods, from milk to alcohol. The administration cast them as retaliation for what it calls Canada's unfair treatment of American dairy, alcohol and automakers. Tellingly, the list spares energy, potash and critical minerals -- all things the U.S. urgently needs from us right now, along with goods already captured by the separate steel and auto tariffs. Canada has refused to move on the list of a dozen or so irritants that U.S. Trade Representative Jamieson Greer presented last year, insisting instead that Washington first lift its punitive tariffs on our steel, aluminum, lumber and autos before serious negotiations can begin. The problem for Canada is that it is not clear what our overall strategy is, other than to rag the puck and hope that a stinging defeat in November's midterm elections make Mr. Trump willing to compromise. Also, now is a good time to drive a hard bargain, since Mr. Trump has landed himself in a real pickle in Iran.