Among likely voters, Clinton draws 43 percent support to 37 percent for Trump, 9 percent for Libertarian nominee Gary Johnson, and 3 percent for Green Party nominee Jill Stein. When the choice is limited to the Democratic and Republican nominees, Clinton's lead grows to seven percentage points, 48 percent to 41 percent.
Her margins have fallen only slightly since the last NBC/WSJ poll in early August, after both parties had staged their national conventions. That indicates Trump has failed to substantially ease doubts about his suitability for the Oval Office, while voters recalibrate their desire for dramatic change as Election Day draws closer.
Respondents "revealed a hardening of personal dislike and professional uncertainty about Donald Trump," said Democratic pollster Peter Hart, who conducts the NBC/WSJ survey with Republican counterpart Bill McInturff. "Voters see Hillary Clinton as safe and smart. In this year, it looks like a winning hand."
The three presidential debates, beginning next Monday night at Hofstra University in New York, give Trump an opportunity to shake up the underlying structure of the race. But McInturff noted: "Something that does not yet exist in this campaign would have to happen."
Most voters continue to look askance at both candidates. Since May, however, views of Clinton (now 37 percent positive, 52 percent negative) have grown slightly more favorable, while views of Trump (28 percent positive, 61 percent negative) have grown slightly less favorable.
On issues, voters prefer Clinton over Trump by 50 percent to 39 percent on "dealing with immigration," while splitting evenly (44 percent Clinton, 43 percent Trump) on handling terrorism and homeland security. On the economy, the billionaire businessman holds a 46 percent to 41 percent edge.
But the poll shows Clinton, a former First Lady, senator, and Secretary of State, with powerful advantages over Trump on "being knowledgeable and experienced enough to handle the presidency" (60 percent to 23 percent), and "having the right temperament to be president" (56 percent to 23 percent). Voters prefer Trump on "being honest and straightforward" by 41 percent to 31 percent, down from his 16-percentage point edge on that quality in June.
Voters choose Clinton by a two-to-one margin, 51 percent to 25 percent, on "being in charge of our nuclear weapons," and by 48 percent to 33 percent on "being a good Commander-in-Chief." Though Trump has cast himself as the candidate of change, voters pick Clinton narrowly (44 percent to 38 percent) on "changing the country for the better."
Indeed, the approach of the election and the choice they face has altered voters' opinions about how much change they want. Some 49 percent say they want a president to bring "major changes" even if those changes can't be predicted, while 47 percent prefer "a steady approach" even if that means fewer changes. That near-even split contrasts with a solid margin in July, when voters preferred "major changes" by a 56 percent to 41 percent margin.
In the battle for Congress — where Republicans currently control both the House and Senate — voters express a narrow preference for Democrats, 48 percent to 45 percent.
The telephone poll of 1,000 registered voters, conducted Sept. 16-19, carries a margin for error of 3.1 percentage points. Among the 922 respondents deemed "likely voters," the margin for error is 3.23 percentage points.
—By CNBC's John Harwood. Follow him on Twitter: @JohnJHarwood
CORRECTION: This story has been updated to show Libertarian presidential candidate Gary Johnson is drawing 9 percent of support among likely voters.