By BOB SALSBERG and SHANNON YOUNG
SPRINGFIELD, Mass. (AP) -- Democratic U.S. Senate candidate Elizabeth Warren won her party's overwhelming endorsement on Saturday, shutting out a potential primary election opponent and becoming the presumptive nominee to face Republican Sen. Scott Brown in what is expected to one of the nation's most expensive and closely-watched Senate races.
Warren won the votes of 95.7 percent of the more than 3,500 delegates to the state Democratic convention, the largest margin of any candidate in a contested race in the party's history.
Marisa DeFranco, an immigration attorney from Middleton, had waged a longshot campaign for Senate but finished far below the 15 percent she needed under party rules to get on the September primary ballot.
"Let's get started on this," a jubilant Warren said moments after the vote, adding that she looked forward to debating Brown.
For Warren, the gathering of party loyalists presented an opportunity to regain momentum for her campaign after struggling for weeks to put behind her a controversy over her claims of Native American ancestry. On Saturday, she took clear aim at Brown.
"So how does a Wall Street, big oil, Mitt Romney Republican plan to win?" Warren asked delegates in her speech before the vote.
"His answer is to talk about anything except how he votes on jobs, education, the environment, oil subsidies, or
"Well I say this, if that's all you've got, Scott Brown, I'm ready," Warren said.
"And let me be clear: I am not backing down. I didn't get in this race to fold up for the first time I got punched," she added.
Warren also invoked the memory of the late Democratic Sen. Edward Kennedy, who for 47 years held the seat that Brown won in a special election in 2010.
"It's a long way from Ted Kennedy to Scott Brown," she said.
In the days leading up to the convention, Warren made perhaps her most concerted effort to address several weeks of questions about her past listing of Native American ancestry, which she has not documented.
First, Warren acknowledged that she had told Harvard Law School and her previous employer, the University of Pennsylvania, of her Native American heritage, but said she did so after she was hired and that it had never been a factor in advancing her academic career.
In a series of interviews on Friday, Warren also provided more detail about the "family lore" that had convinced her of Native American ancestry. She said her mother and father had been forced to elope because her father's parents did not approve of her mother being part-Cherokee and part-Delaware.
Democrats have pointed to recent polls that show an extremely close contest between Warren and Brown and suggest that voters have been little moved by the heritage controversy. But Republican party leaders said they had no intention of backing off on the issue.
The Democrats chose "a deeply-flawed candidate whose campaign has been in free fall for the last five weeks," said Peter Blute, a former congressman and the state GOP's vice chair.
"She has refused to come clean with the full facts and her story has shifted so much in the last five weeks it's difficult to take anything she says seriously," said Blute, who met with reporters across the street from the MassMutual Center, the convention site.
DeFranco had little name recognition, no paid staff and through the first quarter of the year had raised just over $41,000 for her campaign, compared to the $15.8 million that Warren's campaign had pulled in. DeFranco asked delegates to give her enough votes to force a "good and healthy primary," saying it would make the party stronger.
As late as Saturday morning, Democratic state party chair John Walsh had been predicting that DeFranco would meet the 15 percent threshold, though that may have been an effort to lower expectations for Warren in the event of a less resounding endorsement.
The day's most fiery speech came from Gov. Deval Patrick, who broke an earlier pledge of neutrality in the race by endorsing Warren earlier in the week. He said the party must get tough if they want to keep the White House and send a new Massachusetts senator to Washington.
"It's time for Democrats to grow a backbone and stand up for what we believe," Patrick told the delegates.