Among participants in the Concord Monitor poll, 22 percent said they would vote for Clinton if the primary was held now, and 21 percent said Obama. That put them slightly ahead of former North Carolina Sen. John Edwards, who was at 16 percent.
Last month, a Monitor poll showed Clinton leading Obama by 23 percentage points.
"I'm not surprised because Barack Obama got five days of constant media attention in New Hampshire," said Jim Demers, a Democratic activist who accompanied Obama throughout his visit. "Obama has demonstrated to the people of New Hampshire that he's a top tier candidate."
On the Republican side, former New York Mayor Rudy Giuliani and Arizona Sen. John McCain are about even, with Giuliani at 26 percent and McCain at 25 percent. Massachusetts Gov. Mitt Romney is next with 10 percent.
The telephone poll of 600 likely voters was conducted Monday through Wednesday by Maryland-based Research 2000 and had a sampling margin of error of plus or minus 4 percentage points. The likely voters for the Democratic and Republican primary totaled 400 respondents each. For those questions, the margin of error was plus or minus 5 percentage points.
In hypothetical general election matchups, Giuliani has a slight lead over Clinton, while Clinton and McCain are about even. Obama is slightly ahead of both Giuliani and McCain. Edwards is tied with McCain and about even with Giuliani.
"There are a lot of independents. These are the same people who loathe Bush, loathe the Iraq war," said Del Ali, president of Research 2000. "But deep down, they don't like Hillary Clinton."
The numbers don't mean much roughly a year before the primary, some experts cautioned. President Bush, for example, held a double-digit lead over McCain in a New Hampshire poll nine months before the 2000 primary.
"You will have this tremendous amount of energy and motion to secure the allegiance of about 5,000 people," said Charlie Arlinghaus, president of the Josiah Bartlett Center for Public Policy. "And nobody else is going to start paying attention until after the summer."