Washington (CNN)—Since announcing his campaign in late June, Donald Trump has quickly leapt to the top of the Republican field, leading recent polls nationally, in Iowa and in New Hampshire. And now, for the first time in CNN/ORC polling, his gains among the Republican Party have boosted him enough to be competitive in the general election. The poll finds Democratic frontrunner Hillary Clinton ahead of Trump by just 6 points, a dramatic tightening since July. Trump is the one of three Republican candidates who have been matched against Clinton multiple times in CNN/ORC polling to significantly whittle the gap between...