According to the poll, 39% of voters, including 21% of Democrats and 43% of independents, say they are less likely to vote for Clinton as a result of her exclusive use of a private email account to conduct business while secretary of state. Nearly six in 10 Republicans agree.
Back in April, 34% of voters said they were less likely to back Clinton because of her email use. Among independents, the share saying her email use makes them less likely to back her has climbed 14 points, among Democrats, it's up 8 points.
But Clinton still tops Republican front-runner Trump when the two are tested in a hypothetical general election matchup among those likely to cast a ballot in next year's presidential contest, with Clinton at 50% to Trump's 42%.
Bernie Sanders, the Vermont senator who leads Clinton in the race for the state's Democratic primary votes, fares better against Trump, 57% to 37%, as does Vice President Joe Biden, who is mulling a run for the Democratic nomination. Biden tops Trump 56% to 37%.
Clinton fares worse than the other two Democrats among independents, running at 41% to Trump's 42% among that group, while both Biden (46% to Trump's 37%) and Sanders (48% to Trump's 39%), beat the real estate mogul handily among political independents.
New Hampshire has backed the Democratic candidate for president in each of the last three elections, and in 2000, it was a crucial swing state, with Vice President Al Gore ultimately losing by just 1% of the vote.
None of the other Republican contenders for the presidency were tested in the poll.
When asked about which out of three different types of work experience produce the best president, 32% of New Hampshire voters say service as a governor is the best preparation, 26% say being elected to the U.S. Senate or House of Representatives is best, and 20% say someone who never held elective office is best. Republicans are most likely to say the best presidents come from those who have never been elected, 31% think so, and are least likely to say experience in the Senate or House is the best preparation (14%).
The CNN/WMUR poll was conducted by the University of New Hampshire Survey Center by telephone from Sept. 17 through 23. The poll includes interviews with a random sample of 820 residents of New Hampshire, including 43 who say they are likely to vote in the presidential election in 2016. For results among the sample of likely 2016 voters, the margin of sampling error is plus or minus 3.6 percentage points.