Sanders had led in nearly every New Hampshire poll from the beginning August until the first Democratic debate in October. Since then, polling has shown a tight battle between the two leading Democratic candidates in the only early voting state where Clinton does not hold a significant lead.

Eighty-three percent of respondents said they had a favorable opinion of Vermont senator, compared to just 9 percent that had an unfavorable opinion. Clinton, meanwhile, was viewed 68 percent favorably to 24 percent unfavorably by likely Democratic primary voters.

Dr. Andrew Smith, director of the UNH Survey Center, told Boston.com that Sanders’ popularity is “almost unheard of” this far into the campaign.

“I have never seen favorabilities for any candidate this high at this point in the primary,” Smith said, noting that Sanders’ net favorability has only increased since he entered the race.