The Senate race in New Hampshire between Democratic incumbent Jeanne Shaheen and Republican challenger Scott Brown is a dead heat, with Shaheen holding a 3-point lead, according to a Suffolk University/Boston Herald poll released Monday. Shaheen’s lead is within the poll’s 4.4 percentage point margin of error.

The poll shows the race tightening since June, when Shaheen led Brown, 49 percent to 39 percent in the last Suffolk University/Boston Herald poll. A WMUR Granite State Poll taken in August also showed the race a dead heat. Shaheen’s 49 percent favorable rating is higher than Brown’s 39 percent.  

“Despite her higher personal popularity, Shaheen’s forty-nine percent vote share has not increased since the last Suffolk poll, taken in June,” said David Paleologos, director of the Suffolk University Political Research Center in Boston. “With no third-party candidate on the ballot, she’ll be looking to earn the support of one to two of the remaining six points to reach the critical 50 percent mark. Otherwise, she’ll need a strong get-out-the-vote operation to win.”

Shaheen leads among women, 51 percent to 42 percent, while Brown has a 50 percent to 46 percent advantage with men, the poll found. Shaheen fared better with lifelong Granite State residents, 52 percent to 43 percent. Brown, a former U.S. senator from Massachusetts, moved to New Hampshire in April.

The Republican candidate ran an ad claiming Shaheen voted with President Barack Obama 99 percent of the time in the Senate. The spot didn’t sway voters in the poll, with 44 percent saying the ad would make no difference about who they would vote for. Another 17 percent said the ad makes it more likely they will vote for Shaheen while 35 percent said the spot makes it less likely they’ll vote for the Democratic incumbent.  

The poll of 500 likely voters was taken from Thursday through Sunday.