Donald Trump is now the only Republican presidential candidate with a realistic chance of winning the 1,237 votes to clinch the nomination before the national convention this summer. But getting there will be a tough undertaking, and one that leaves little room for error. Trump's commanding victory in New York, where he won more than 60% of the vote and the vast majority of the 95 delegates up for grabs, marked a turning point in the delegate race. The Manhattan real estate mogul now has improved his chances of winning the nomination outright, while his chief rival, Ted Cruz, would...