Hillary Clinton and Bernie Sanders have clashed over Wall Street and foreign policy, in the Democratic presidential candidates' first one-on-one debate.
Mrs Clinton cast him as an idealist who will not get things done and Mr Sanders accused her of being too tied to the establishment to achieve real change.
The TV debate in New Hampshire was their first since the Democratic race was whittled down to two this week.
Without a third person on stage, the policy differences were laid bare.
The former secretary of state said Bernie Sanders' proposals such as universal healthcare were too costly and unachievable.
And she went after her rival aggressively over his attempts to portray her as being in the pocket of Wall Street because of the campaign donations and the fees she had received for after-dinner speeches.
"It's time to end the very artful smear that you and your campaign have been carrying out," she said.
Mr Sanders, a senator of Vermont, used a favourite attack line against her, that she backed the Iraq War, but she questioned his foreign policy expertise.
The debate comes five days before the second state-by-state contest in the battle for the presidential nominee, in New Hampshire on Tuesday.
Other highlights include:
She represents the establishment, I represent ordinary Americans, said Mr Sanders
By standing up to big money interests and campaign contributors, we transform America, he said
Mrs Clinton was asked to release the transcripts of all her paid speeches - she said she would look at it
He demanded the break-up of the big banks but she said her regulatory policies would be tougher on Wall Street
Asked what she stood for, she named clean energy, the affordable care act and getting paid family leave
He said he was stronger because "Democrats win when there is large turnout" and he could enthuse young people
Despite the tensions over policies, the debate ended on a warm note, when Mrs Clinton said the first person she would call would be Mr Sanders, if she won the nomination.
When in doubt, say you're with Barack Obama. It was telling in this last debate before the New Hampshire primary that both candidates, when forced to defend themselves on grounds where they felt vulnerable, turned to Barack Obama for protection.
Early in the debate, when pressed by the Vermont senator on her ties to Wall Street, Mrs Clinton noted that Mr Obama had taken donations from the financial industry and still passed comprehensive reform. He did it because he was a "responsible president," she said.
Later in the evening, Mr Sanders was pressed on his foreign policy views and willingness to normalise relations with Iran. He noted that he agreed with Mr Obama on the issue, despite Mrs Clinton criticising the then-senator in 2008 for being "naive".
The Democratic president is still overwhelmingly popular among Democrats - and he proved to be a reassuring refuge.
But if this, in fact, revealed where the candidates were weakest, that can only be good news for Mr Sanders. Polls overwhelmingly show Democrats are much more concerned about the economy than they are about international affairs.
The debate was their first without the presence of the former governor of Maryland, Martin O'Malley, who quit the race on Monday night.
He was a distant third in the first state to vote, Iowa, where Mrs Clinton narrowly beat Mr Sanders after a prolonged count.
Mr Sanders holds a big lead in polls in New Hampshire, which borders the state where he is a senator, Vermont.
Both Republican and Democratic parties will formally name their presidential candidates at conventions in July.
Americans will finally go to the polls to choose the new occupant of the White House in November.