David Goldman, Associated Press
Democratic presidential candidate, Hillary Clinton listens as Democratic presidential candidate, Sen. Bernie Sanders, I-Vt, answers a question during a Democratic presidential primary debate hosted by MSNBC at the University of New Hampshire Thursday, Feb. 4, 2016, in Durham, N.H.

DURHAM, N.H. — Fireworks flying in their first one-on-one debate, Hillary Clinton accused Bernie Sanders on Thursday of subjecting her to an "artful smear" while Sanders suggested the former secretary of state was a captive of the political establishment.

It was a markedly more contentious tone than the two candidates set when they last debated before the presidential voting began in Iowa, and it signaled how the race has tightened five days ahead of the first-in-the-nation primary next Tuesday.

The two argued over ideas, over tactics and over who has the liberal credentials to deliver on an agenda of better access to health care, more affordable college and more.

It was Clinton who went on the offensive, saying he could never achieve his proposals. Then she took after the Vermont senator for his efforts to cast her as beholden to Wall Street interests because of the campaign donations and speaking fees she's accepted from the financial sector.

"It's time to end the very artful smear that you and your campaign have been carrying out," she said.

Sanders, for his part, suggested her loyalties were colored by a reliance on big corporate donors.

"Secretary Clinton does represent the establishment," he said. "I represent — I hope — ordinary Americans."

Clinton may say the right things, he suggested, but "one of the things we should do is not only talk the talk but walk the walk."

On policy matters, Clinton called Sanders' proposals "just not achievable," while Sanders countered that Clinton was willing to settle for less than Americans deserve.

"I do not accept the belief that the United States of America can't do that," Sanders said of his plan for universal health care and of his efforts to take on "the rip-offs of the pharmaceutical industry."

Clinton insisted they both wanted the same thing; "the disagreement is where do we start from and where do we end up."

The race for the Democratic nomination, once seen as a sure thing for Clinton, intensified this week after Sanders held the former secretary of state to a whisper-thin margin of victory in Iowa's leadoff caucuses. The tone of their back-and-forth has become increasingly sharp, and the candidates agreed to add four more debates to the primary season schedule, including Thursday's faceoff in Durham.

The debate is the last before Tuesday's first-in-the-nation New Hampshire primary, and Sanders holds a big lead in polls in the state.

In fresh evidence of the tightening race, Clinton reported that her campaign had raised $15 million in January — $5 million less than Sanders and the first time she's been outraised by her opponent. Her finance director called the numbers "a very loud wake-up call" in a fundraising email to supporters.

Heading into the debate, Sanders was eager to lower expectations for his finish in New Hampshire, casting himself as an underdog against "the most powerful political organization in the country."

Clinton, for her part, signaled her determination to at least narrow the gap before Tuesday's vote in the state where she defeated Barack Obama in 2008 before ultimately losing the nomination to him. Her prospects are much stronger in primaries and caucuses after New Hampshire, as the race moves on to states with more diverse electorates that are to her advantage.

The two campaigns have even skirmished this week over why Sanders is doing so well in New Hampshire polls. His campaign accused Clinton's of insulting New Hampshire voters by suggesting they only support the Vermont senator because he's from a neighboring state. That was after Clinton's campaign manager referred to New Hampshire as Sanders' "backyard."

Clinton's campaign also criticized Sanders' camp for what it said were misleading ads that suggest the senator received the endorsement of two newspapers that have not backed his bid for the White House. Sanders countered that the ads didn't say he'd been endorsed but merely passed along "nice" words the newspapers had written about him.

The Durham debate will be the first faceoff for Clinton and Sanders since former Maryland Gov. Martin O'Malley dropped out of the race after a poor showing in Iowa.

Clinton's razor-thin win in Iowa was the latest twist in an election campaign that, until recently, had been dominated by the crowded and cacophonous field of Republicans, who spread out across New Hampshire this week.

Donald Trump, who finished second in Iowa, stepped up the pace of his campaign and acknowledged he should have had a stronger ground operation in Iowa. Jeb Bush, his campaign lagging, brought in his mom, former first lady Barbara Bush, who praised him as "decent and honest and everything we need in a president."

Benac reported from Washington. Associated Press writer Scott Bauer contributed from Madison, Wisconsin.

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