A majority also think the private email server endangered national security.
Walker, who led for months, is on the decline, with Carson surging to second.
Julian Hattem 07/27/15 09:18 AM EDT
Most voters support the Iran deal, according to the poll.
A poll finds Trump would siphon significant support from Bush in a three-way race with Clinton.
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.