Brown is suggesting that the woman who made a national reputation as a fierce advocate for the middle class and consumers is a phony.
Warren, meanwhile, is urging Massachusetts voters to look beyond their affection for Brown to consider the votes he has cast and the national consequences of an election that could help return the Senate to Republican control.
Brown on Monday launched the most brutal salvo yet in a campaign that until recently was notable for its civility. His new television ad highlights the controversy over Warren’s unproved claim that she is of Native American heritage. It also raises the possibility — also unproved, and denied by those involved in hiring her — that she claimed minority status for professional advancement.
The 30-second spot resurrects what Republicans call the “Fauxcahontas” flap, which had died down since erupting last spring. At the end of the ad, an interviewer asks Warren whether anything else will come out about her, and the Harvard Law School professor replies, laughing, “You know, I don’t think so, but who knows?”
It amplifies a larger message that Brown has been pounding over and over in recent days, as he has also questioned the size of her Harvard salary and her past work on behalf of an insurance company involved in an asbestos suit.
“The true Elizabeth Warren is coming out and will continue to come out,” Brown said at an appearance Saturday in South Boston, the only part of this deeply Democratic city to support him when he won his Senate seat in a special election two years ago.
Though theirs is the most expensive Senate race in the country, with more than $53 million raised so far, the two candidates made a pact in January to disavow advertising by outside groups. That had helped keep the race more positive and restrained than many others, as Brown sought to maintain his nice-guy image and Warren to tamp down hers as a scold.
Warren launched the first negative ads of the campaign this month, at a time when some Democrats — including former governor Michael Dukakis, the 1988 presidential nominee — were criticizing the candidate and her campaign for failing to connect.
It was a gentle jab at first.
“Scott Brown’s not a bad guy. He doesn’t always vote the wrong way,” Warren said in one of those ads. “But too often, on things that really matter, he’s not with you.” She cited Brown’s opposition to President Obama’s jobs bills, his vote against imposing higher taxes on millionaires and his support for subsidies to oil companies.
But in a fundraising e-mail sent after his new ad appeared on Monday, she was blunter: “We know where Scott Brown stands — and it’s not with the people of Massachusetts. It’s with big money and his Republican buddies.”