The first one-to-one Democratic debate saw Hillary Clinton and Bernie Sanders clashing over Wall Street and foreign policy.
Hillary Clinton cast Bernie Sanders as an idealist who will not get things done and Sanders accused the former Secretary of State of being too tied to the establishment to achieve real change.
The MSNBC 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.
Hillary Clinton said Bernie Sanders’ proposals such as universal healthcare were too costly and unachievable.
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.
Vermont Senator Bernie Sanders used a favorite attack line against Hillary Clinton 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 February 9.
Despite the tensions over policies, the debate ended on a warm note, when Hillary Clinton said the first person she would call would be Bernie Sanders, if she won the nomination.
The debate was their first without the presence of the former governor of Maryland, Martin O’Malley, who quit the race on February 1.
Martin O’Malley was a distant third in the first state to vote, Iowa, where Hillary Clinton narrowly beat Bernie Sanders after a prolonged count.
Bernie 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.