Joe Biden and Sen. Elizabeth Warren (D-Mass.), two of the leading presidential hopefuls, are set to meet Thursday on the debate stage, a platform that will highlight their wildly different styles and messages.

“They’re both very strong but with a different touch,” said former senator Barbara Boxer (D-Calif.), who served in the Senate with Biden and Warren. “Elizabeth connects with you strongly on the issues. Joe connects even more on a personal level. . . . She makes the most passionate argument, but Joe has the added dimension of having a personal touch.”

That divergence began long before they even met. As a young senator in the early 1970s, Biden fought against mandated busing as a path to school integration, arguing for less coercive methods. Warren, as a law student during the same period, wrote her first law review article about why the Supreme Court was wrong to restrict busing.

But their hardest-fought confrontations came during the late 1990s and early 2000s, when credit companies were fighting to make it harder for Americans to declare bankruptcy, complaining that free-spending consumers were irresponsibly using the process to protect themselves.

Biden, whose home state of Delaware was the headquarters of many financial services firms, championed their cause. These firms were among Biden’s top campaign contributors. He even earned the nickname “the senator from MBNA,” a reference to a bank founded in Delaware.

Warren, then a professor, blasted Biden by name in a 2002 New York Times piece for playing a key role in what she called an “unconscionable” bankruptcy bill.

In a paper in the Harvard Women’s Law Review in 2002, she argued that with his “presidential ambitions growing,” women’s groups should oppose Biden because the bill would disproportionately harm women. In her 2003 book, “The Two-Income Trap,” written with Amelia Warren Tyagi, she added that he was a “sellout” when it came to women.

Warren was Biden’s opposite, a fighter where he was a backslapper, an activist who once said of battling financial institutions that she wanted “plenty of blood and teeth left on the floor.” She was already a top bankruptcy expert, winning a Harvard Law School professorship in part because of her research on how middle-class families were going broke at alarming rates. She saw the bankruptcy system as a safety net, allowing families to erase debt and start fresh.

The two clashed again in 2005 when the bankruptcy bill made it to the Senate Judiciary Committee, on which Biden was a senior member. Sitting at the witness table, Warren listened as Biden pushed her to talk about the role government should play when families cannot pay their bills.

Biden referred to Warren as “professor” twice and, before she spoke, characterized her argument as “very compelling and mildly demagogic.”

He asked who should foot the bill when consumers can’t pay. If Warren believed the chief victims were struggling families doing their best to stay afloat, Biden also sympathized with companies, including small businesses, that were getting shortchanged through no fault of their own.

“Is it the responsibility of the gas company and the drugstore and whoever else you name to make sure that these people do not have to make these hard choices?” Biden asked. “Or is that the responsibility of the government or the people at large?”

Warren did not directly answer the question, a tactic she continues to employ, saying the real solution is an economy where Americans are doing better.

“We need fewer families to need to turn to the bankruptcy system,” Warren said, pointing to health-care costs as a major factor. Until the health system can be fixed, she argued, Americans need the option of a generous bankruptcy system.

Jared Bernstein, Biden’s chief economist during the early years of Barack Obama’s presidency, said there was “no question he and Warren were on different sides.”

But he insisted the relationship warmed once Biden became vice president. In the bankruptcy fight, Biden was representing his state’s interests. His prism broadened significantly when he joined the administration, Bernstein said.

The Obama team, after all, immediately confronted a devastating financial meltdown that threatened middle-class families across the country. Warren was tapped by then-Senate Majority Leader Harry M. Reid (D-Nev.) to come to Washington to help keep watch over the distribution of bailout money, ultimately becoming a resource for the Obama team rather than an adversary.

Obama tapped Biden to head a task force aimed at improving the lot of the middle class, and Biden saw Warren as an ally. He supported her successful push to create an agency charged with protecting consumers from deceptive financial practices.

“What I got to see was a relationship that was really forged on respect,” said Terrell McSweeny, a former Biden aide. “I think they had a lot of shared perspective in terms of focusing on getting the economy back on track.”

Still, some Warren allies play down Biden’s role in winning passage of the Dodd-Frank law, the sweeping bank overhaul measure that established the Consumer Financial Protection Bureau (CFPB) championed by Warren.

Some liberal Democrats still say Biden is too close to corporate interests, and some moderates say they are uncomfortable with Warren’s attacks on the status quo.

“The president said, ‘Do you think she wants to be a senator?’ ” Frank recalled. “And I said, ‘No, I think she wants your job, but she knows she’s got to start somewhere.’ ”

It is unclear whether Biden played a role in recommending or discouraging Warren’s appointment as leader of the CFPB. Facing forceful opposition from Republican senators, Obama ultimately declined to nominate her — a blow to Warren, but one that set her on course for the Senate.

When Warren won her 2012 Senate campaign, it was Biden, in his role as vice president, who presided over her swearing in. “You gave me hell,” Biden joked to Warren, referring to their previous skirmishes.

Biden harbored no ill will toward Warren, and according to former senator Ted Kaufman, a onetime Biden aide who took over his Senate seat after he became vice president. That fits Biden’s tendency to view political adversaries as friendly opponents rather than implacable enemies, Kaufman said

“I think at the end of the day, it’s entirely consistent with the way Vice President Biden approaches relationships,” McSweeny said. “In his heart, I think he believes they are aligned on helping the middle class. Whether they agree on every solution is different, but they are trying to address the same issues.”

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