Over the past couple of weeks, Donald Trump has become the presumptive Republican nominee and Hillary Clinton continues to inch closer to the magic number of delegates she needs to lock up the Democratic contest. Clinton continues to lead Bernie Sanders in our national tracking poll (she is up by 14 points in this week’s results). Attention is now rapidly moving to the hypothetical match-up between the leading candidates with an emphasis on a Clinton and Trump contest. In this week’s poll, Americans are nearly split between their choice of Trump or Clinton; her margin over Trump narrows from 5...