It’s not exactly Donald Trump’s Reykjavik, but he has done the right thing by calling off the misconceived summit with Kim Jong-un.The North Koreans have been yanking our chain over the last week or so, presumably trying to establish their leverage and begin a negotiation over the negotiation. They seemed to make some progress, with Trump saying the other day that maybe we could settle for something short of complete, verifiable denuclearization, which is supposed to be our core demand. The president may have tempted the North Koreans into the gamesmanship by occasionally seeming over-eager to take credit for a...