Far from irreparably fracturing the GOP, Donald Trump is quickly winning the backing of many of the party’s top elected officials, with senators returning to Washington this week pledging their support for him as their nominee. Outside of Washington, Republican voters are likewise warming to Mr. Trump, and are decidedly cool to calls to recruit a third-party alternative to Mr. Trump and likely Democratic nominee Hillary Clinton, saying there’s too much at stake to give Democrats another four years’ control of the White House. “I think it’s a great idea, but not for this particular election,” said Gregg Mattox, standing...
