The new numbers come as the Vermont senator claims his first slim lead in the crucial state of Iowa and extends his lead in New Hampshire -- posing a threat to the Democratic frontrunner in the two first crucial contests.
The former Secretary of State's national lead has narrowed from 20 points in the same poll in early December.
Earlier on Tuesday, a Quinnipiac poll showed Sanders leading Clinton for the first time in the Hawkeye state. With 49 percent support, Sanders is seeing the highest support in any Iowa poll so far. Clinton is polling at 44 percent support, a 7-point drop for her since the last Quinnipiac poll conducted a month ago.
"She is in serious trouble,” Sanders said speaking to reporters in Pleasantville, Iowa yesterday. “And I think a candidate who was originally thought to be the anointed candidate, the inevitable candidate is now locked in a very difficult race here in Iowa and in New Hampshire.”
The Clinton campaign has acknowledged that the former secretary of state is in for a tough fight in the early voting states against the Vermont senator. Last week, the campaign sent fundraising emails about the tight polls, including one from Campaign Manager Robby Mook with the subject line "nervous.”
When asked by ABC News’ Cecilia Vega on Monday in Waterloo if she was feeling nervous about Iowa, Clinton showed optimism.
“I’m feeling great,” she said, “You always have to work hard and be running hard.”
In a statement Tuesday, Clinton's campaign said: "Since the campaign started, we have said this race will be a competitive, tough race that would tighten and we’d have to earn the nomination. We have built a tremendous grassroots organization in Iowa fueled by enthusiasm for Hillary Clinton and her record, that is set to compete and win.”