The new poll, mostly conducted before Sunday night's debate, found Sanders' support has grown by 10 points since a late-November/early December CNN/WMUR poll
, which found Sanders holding 50% to Clinton's 40%.
New Hampshire Democrats' views on the race are solidifying as well, with 52% saying they have definitely decided who they will support, up from 36% who felt that way in early December. Among those voters, Sanders holds an even broader 64% to 35% lead.
But the Vermont senator's support rests heavily on groups whose participation in New Hampshire primaries is less reliable -- notably younger voters and those who aren't registered Democrats.
There are some signs in the poll that the increasingly contested Democratic race is gaining attention among the state's undeclared voters, who are not registered as members of any party and are able to choose which party's primary they will participate in. In the December poll, 38% of undeclared voters who said they planned to vote said they would likely participate in the Democratic primary, a figure that is up to 48% in the new poll.
Those undeclared voters are critical to Sanders' support: 70% in the new poll say they plan to vote for him, 25% Clinton. Among registered Democrats, it's 50% Sanders to 41% Clinton. Still, that represents an increase for Sanders among registered Democrats. The December poll found him trailing Clinton, 47% to 40%, among that group.
Sanders' rise in the poll comes as New Hampshire voters' focus on national security has faded.
The previous poll -- conducted in the aftermath of the terrorist attack in Paris and as the attack in San Bernardino, California, unfolded -- found 23% of likely Democratic voters calling foreign policy and national security their top issue. That faded to 13% in the new poll, while the share naming the economy and jobs their top priority has climbed from 18% to 26%.
On the economy, New Hampshire voters now clearly give Sanders the edge over Clinton as the candidate more trusted to handle it: 57% say Sanders would best handle it vs. 33% for Clinton.
That's a massive shift since last summer, just as Sanders' campaign began to gain traction. In that poll, 37% said they preferred Clinton on the economy, 28% Sanders, and 22% were unsure which candidate would best handle that issue. In the new poll, Clinton maintains a broad lead over Sanders as the more trusted candidate when it comes to ISIS, 55% Clinton to 26% Sanders, about the same as in early December.
Sanders also has astonishingly high favorability ratings among those likely to vote in New Hampshire's Democratic primary, and is broadly seen as the candidate with the "personal characteristics and qualities that you think a president should have."
Overall, 91% say they have a favorable view of Sanders, while just 2% have an unfavorable opinion. That's improved since December, when 83% had a positive take on the neighboring state's senator. Almost 6-in-10 say they see Sanders as the more presidential candidate in the field, compared to 33% for Clinton.
While Clinton is also viewed positively, her numbers lag well behind Sanders' ratings, with 65% saying they have a favorable impression of the former secretary of state. The poll suggests Clinton continues to be dogged by questions about her honesty, with the share saying she is the least honest in the field now at 55%, up from 46% in December.
The CNN/WMUR poll was conducted by the University of New Hampshire Survey Center by telephone from January 13-18. The poll includes interviews with a random sample of 927 adult residents of New Hampshire, including 420 who say they plan to vote in the Democratic presidential primary. For results among the sample of likely Democratic primary voters, the margin of sampling error is plus or minus 4.8 percentage points.