The effect on presidential choice, however, appeared to be minimal, and Roberts, the Republican pollster, suggested that could spell trouble for Trump. After the attack, CNBC asked which candidate has the best policies for "dealing with terrorism and homeland security." The 408 respondents to that question (half the sample, with a margin of error of 4.8 points) gave Trump only a slight edge of 40 percent to 38 percent. Roberts said that going back to 2002, Republican candidates typically hold 10 to 36 point leads over Democrats on national security issues.
"That's a major red flag for Trump," said Democratic pollster Campbell.
Among the challenges facing Clinton, while she is seen as best for the middle class by a 43 percent to 32 percent margin, the actual middle class is less sure. Among those with incomes from $50,000 to $75,000 and among blue collar workers, Clinton and Trump are tied on the middle-class question.
Clinton also faces a large block of Sanders voters choosing neither. She'll have to bring them on board, and has just a 3-point lead among independents, 35 percent of whom choose neither candidate.