HANOVER, N.H. — In response to accusations he’s going negative, Vermont U.S. Sen. Bernie Sanders defended his latest ad that appears to bash Hillary Clinton’s ties to Wall Street, saying tonight at a Dartmouth College news conference that it’s not meant to be inflammatory.

In the ad, Sanders states, “There are two Democratic visions for regulating Wall Street. One says it’s OK to take millions from big banks and then tell them what to do.”

Critics have said Sanders has broken his pledge to steer clear of attacks during his campaign.

But the senator said it was not a pointed statement about Clinton.

“This is not a negative ad,” he said at a news conference preceding a gathering at Dartmouth College. “Everybody knows there are two divisions.”

“It’s clear,” he said, “which side I’m on.”

Sanders, who is gaining on Clinton in recent polls, also received an endorsement from U.S. Sen. Paul G. Kirk Jr., a past chairman of the Democratic National Committee.

“I had the privilege of serving briefly with Bernie Sanders in the United States Senate and I quickly learned that he is who he is,” Kirk said. “Plain spoken and an authentic patriot who wears his passion for a better America on his sleeve.”

Sanders, who has seen high numbers in the New Hampshire polls, is now nipping at Clinton’s heels in Iowa.

Clinton leads Sanders by only 2 percentage points in the new Des Moines Register/Bloomberg Politics poll, down from 9 percentage points last month.

“What has happened over the last nine months is literally something I never, ever, ever would have dreamed of,” Sanders said.

Hundreds of students gathered in the school auditorium — some to show their support, and some to get a better feel for the candidate before the primary rolls around.

Many said the success of the Sanders campaign comes as a surprise.

“I think that he’s definitely got a significant chance to be the candidate and be elected president,” said John Patrick Lewis, a 22-year-old student. “Astronomically better chance than people originally thought.”