According to her campaign, more than 90 percent of the contributions came from donors who gave less than $250, and nearly 8,000 donors gave this past quarter.

Shaheen's campaign finance director, Andy Darkins, said the campaign is "proud to have so much grassroots support" for her efforts in the Senate

“The support our campaign has received so far shows that we’re going to have the resources we need to run an effective, winning campaign," he added.

Though she's running in a swing state where Republicans believe they could have a shot at her seat without President Obama at the top of the ticket, Shaheen has shown resilience. An April poll showed leading two of her potential Republican challengers, state Senate Majority Leader Jeb Bradley and former Massachusetts Sen. Scott Brown.

That poll did give her less than 50 percent support against both of the candidates, however, indicating there may be an opportunity for a Republican to make inroads against her. No Republican, however, has yet entered the race.