Her unfavorable rating has jumped 8 points since she announced her White House bid.
Survey also shows Biden could be a strong Democratic challenger.
The poll finds Hassan up 45-44 in a hypothetical 2016 Senate matchup.
Trump was the preferred GOP presidential nominee for 15 percent of respondents.
Christie's job approval rating at home has been trending downward for months.
Voters in Florida, Ohio and Pennsylvania are skeptical of her integrity, a poll finds.
A packed field of candidates including Bush, Rubio and Carson are close behind.
Most Iowa voters wouldn’t mind an ex-president playing a prominent role in the White House.
The governor poses the most formidable challenge to Ayotte's reelection efforts.
The survey was conducted on behalf of conservative super-PAC American Crossroads.