Straightforward. Awesome. President. These are a handful of phrases participants used to describe Donald J. Trump in Frank Luntz's focus group Wednesday evening, nearly all supporters of the current Republican frontrunner. They were a group filled with emotion. For one man, a changing of the guard from Obama to Trump is the stuff of which political dreams are made. "I want Trump to look at Obama on Election Day and go, 'You're fired.'" But in the wake of Trump's call this week to ban all Muslims from entering the country, which has drawn rebukes from nearly every Republican in Washington,...