Republican pollster Bill McInturff, who conducts the NBC/WSJ poll with Democratic counterpart Peter Hart, cautioned that it's too early to say the results signal a definitive shift in the race.
"When you see a number this different, it means you might be right on top of a shift in the campaign," McInturff said. "What you don't know yet is if the change is going to take place or if it is a momentary 'pause' before the numbers snap back into place."
As for whether the survey shows Republicans pulling away from the billionaire businessman after his accusations that President Bush had lied before the Iraq War and failed to keep America safe, McInturff added, "One poll post-Saturday debate can only reflect there may have been a 'pause' as Republican voters take another look at Trump. This happened earlier this summer and he bounced back stronger. We will have to wait this time and see what voters decide."
Republican strategists opposed to Trump have held out hope that a "ceiling" on his potential support might allow a rival to best him for the nomination once the Republican field thins. The NBC/WSJ poll provides some encouragement for them: just 56 percent of Republicans say they can envision supporting him, down from 65 percent in January. By contrast, 70 percent say they can envision supporting Rubio, and 65 percent say they can envision supporting Cruz.