The poll, conducted by Public Policy Polling for the League of Conservation Voters, found Shaheen leading Brown 47 percent to 39 percent. That widens her advantage to 8 points, up from 3 points on PPP's survey last month.
The survey also noted that Shaheen takes the lead 41 percent to 37 percent among crucial Granite State independent voters, which she and Brown previously split. The share of voters viewing Brown unfavorably also rose by 7 points over last month's survey, although the share of those who view him favorably has remained stable.
The New Hampshire Union-Leader reported Friday that Brown, who has publicly flirted with entering the race for months, had begun making private calls to prominent New Hampshire Republicans. This week Brown renewed a contract with Fox News amid the Senate rumors.
The poll surveyed 686 New Hampshire voters on Feb. 19-20 and had a margin of error of 3.7 percentage points.