PAC attacks Brown as Mass. Senate race heats up

The ad, from a group named Rethink, comes on the same day that Elizabeth Warren, who leads in the race for the Democratic nomination to face Brown, launched her first television ad in the state. It also comes on the heels of an ad buy by Karl Rove's American Crossroads PAC that ties Warren and the Occupy Wall Street movement together.

"As voters learn what Scott Brown's record in Washington really looks like, it will become clear he's not on the side of Massachusetts families," said Liz Morningstar, senior strategist for the PAC, in a press release. "Rethink seeks to show Massachusetts voters that what Scott Brown says he'll do for people in our state is very different from the way he's actually voting in Washington."

The ad buy, which will link from Massachusetts news pages, includes an anti-Brown website and two Web videos. The first accuses Brown of leveraging his vote to win concessions for donors, including Wall Street banks that contributed more than $1 million to his campaign. The second attacks Brown votes on an extension of unemployment benefits and for supporting a bill that cut Pell Grant funding.

"As families in Massachusetts struggle to pay the bills, Senator Brown rakes in campaign donations from Wall Street and votes to ease regulations on the financial industry," said Morningstar. "This is politics as usual — not an independent voice for the people of Massachusetts."

Brown's campaign denounced the ad as "mudslinging" by special interest groups.

"The political machine and Beacon Hill insiders are so threatened by his presence as an outsider and independent voice that they haven’t stopped attacking him since his election," said Colin Reed, Brown's communications director. "While the entrenched special interests continue their mudslinging, Scott Brown is concentrating on putting people back to work."

The Massachusetts contest looks to be among the most hotly contested in the 2012 cycle. Brown is a popular centrist who was the first Republican to win a Senate seat in the state for decades, but Warren, a popular figure with the left for her consumer advocacy, should prove a formidable challenge.

Watch the second ad below:

This story was updated at 3:30 p.m.