Donald Trump has taken an unlikely path to winning the GOP nomination for president. And now he's taking an unusual approach to campaigning for the general election that could cost him dearly. The billionaire businessman effectively clinched his party's nomination a full month before Democrat Hillary Clinton did the same. But Trump spent much of the month of May campaigning in states that won't help him win the 270 votes he needs in November. Yes, the California primary and contests in other Western states still loomed. But he was unopposed in those GOP contests, and many Republicans wished he had...