LOWELL, Mass. -- Another Massachusetts Senate debate, another opening question about Elizabeth Warren's native American heritage.
Inside the Tsongas Arena in front of a raucous crowd of over 4,500, NBC "Meet The Press" host David Gregory opened with the contretemps over the ethnic heritage that the Harvard law professor listed in law directories in the 1980s that has consumed much of the attention in one of the nation's most watched Senate races.
Warren calmly explained. Then Sen. Scott Brown shot back, "There's a test you take, and I believe she's failed that test." Gregory then asked about clients of the candidates, who are both lawyers. That set off more charges and counter-charges.
The back-and-forth exchanges, consuming about a third of the debate, show that the contest has gotten increasingly personal. Warren, in a seeming acknowledgement of Brown's personal popularity, has focused on the senator's voting record. Brown has rolled out the native American issue as proof that Warren can't be trusted and has touted his independence from national Republicans.
Brown has tried to distance himself from Republican presidential nominee Mitt Romney, unpopular in Massachusetts, but Gregory tried to pin him down. Brown talked about how bipartisan and independent he is. He finally admitted that he supports Romney, "when it comes to dealing with the economic issues, yes, absolutely." He added that Romney is "out campaigning all over the country. I'm running here in Massachusetts." Brown also praised President Barack Obama.
Warren fumbled a question about which Republican senators she would work with. "Richard Lugar would be one to come to mind," she said, then was quickly corrected by Brown and Gregory, who noted that Lugar lost his party primary. Warren said she was willing to work with Republicans to "revise" Fannie Mae and Freddie Mac, which the government has spent billions to prop up since the housing crisis in 2008.
Brown seized on the blunder to tout his bipartisan credentials, but Gregory pressured him to say whether he would vote for Mitch McConnell as Senate majority leader. McConnell famously said his goal was to make Obama a one-term president.
Brown said he told McConnell that he was "disgusted" with what was happening in Washington. "He's got a lot of work to earn my vote," said Brown.
That answer didn't satisfy Gregory, who ultimately got out Brown to admit he's "undecided" on whom he would vote for.
Warren charged back that Brown was telling Republicans across the country a different story in fundraising pitches that highlight his race as important for the GOP to win Senate control.
Brown started explaining his voting record, which he said that Warren had "misstated," and Warren tried to interrupt. "Excuse me, I'm not a student in your classroom. Please let me respond," snapped Brown to a mixture of boos and applause. It seemed to be a soundbite with lasting power.
The debate moved onto familiar policy territory about taxes and energy, where the candidates have clear differences. Brown wants to extend the Bush-era tax cuts for all earners, while Warren doesn't for the richest. Brown favors continuing oil subsidies; Warren doesn't.
The sharpest policy differences emerged at the end, when they discussed immigration, the war in Afghanistan and the Supreme Court.
Brown said he opposed the Dream Act. "I am in favor of full legal immigration, I don't support it, it's a form of back-door amnesty." He charged that Warren favors drivers licenses for undocumented immigrants (not a federal issue), opposed immigration enforcement and is against "securing our border."
"Senator Brown is right, this is is a big difference between the two of us," said Warren. "I would strongly support the Dream Act."
On the War in Afghanistan, Warren said the troops need to be out now, ahead of Obama's 2014 timeline. "I think that we have always had difficulty with Afghanistan," she said. "We can't stay and rebuild Afghanistan forever." Brown said he supports Obama's timeline, but not the announcement of it.
Brown then said that Scalia was his "model" Supreme Court justice, and the crowd roared. He tried to recover a bit by mentioning four other justices of wildly different ideologies. Warren said her model was Elena Kagan, former dean of Harvard Law.
Brown's Supreme Court gaffe will likely overshadow the candidates' policy differences. After the debate, Warren said she would have liked to talk "even more" about Brown's voting record.
Rep. Barney Frank (D-Mass.) said he was surprised at the opening. "Too little discussion of public policy and too much of a kind of insider politician thing," he said.
RELATED ON HUFFPOST:
How will Donald Trump’s first 100 days impact YOU? Subscribe, choose the community that you most identify with or want to learn more about and we’ll send you the news that matters most once a week throughout Trump’s first 100 days in office. Learn more