Democratic candidates for the US presidency have held their last debate before the nominating elections begin with the Iowa caucuses on 3 January.
The debate was good natured and focused on policy
The discussion was more polite and genial than previous encounters, in which contenders targeted each other.
The candidates outlined their positions on issues ranging from the economy to Iraq, trade, energy and human rights.
Recent polls in Iowa have shown Barack Obama edging ahead of national frontrunner Hillary Clinton.
Dominant themes in the 90-minute debate were Democratic plans to tackle the federal budget deficit by ending the war in Iraq, to halt tax cuts for high earners and to rein in powerful corporations.
Each of the six candidates faced a question over a perceived area of weakness in their bid to become president in national elections scheduled for 4 November 2008.
Sen Clinton said she had "learned a lot" and promised "open and transparent" government, when challenged about criticisms over the Bill Clinton presidential library's failure to release documents from her time as first lady.
Sen Obama is threatening Sen Clinton's lead in Iowa polls
Sen Obama was asked how he planned to deliver a break with the past on foreign policy, when he had little experience and several former advisers to former President Bill Clinton are on his team.
"Hillary, I'm looking forward to you advising me as well," he joked, before saying he planned to restore global respect for America, by "talking not just to our friends but our enemies".
Sen John Edwards, currently third in the polls, stressed his plan to challenge corporate power, saying many of the things Democrats wanted to do on issues such as health care, climate change and trade all "depend on winning this battle".
The polite tone of the debate was a departure from some previous fiery exchanges, and followed concerns that negative campaigning tactics might put voters off.
It came as a senior member of Ms Clinton's New Hampshire campaign team resigned after apologising for bringing up Mr Obama's past drug use - which he had written about in his autobiography.
Ms Clinton apologised personally to Mr Obama ahead of the debate, her aides said.
EARLY PRIMARY TIMELINE
3 Jan: Iowa caucus
8 Jan: New Hampshire primary
19 Jan: South Carolina primary (Rep)
26 Jan: South Carolina primary (Dem)
29 Jan: Florida primary
5 Feb: some 20 states including California, New York, New Jersey
Sen Clinton has seen her lead over Mr Obama eroded in recent weeks, with some polls showing Mr Obama to be slightly ahead in Iowa and also in New Hampshire, which holds its primary on 8 January.
The early primaries are crucial because candidates who do not do well in early elections tend to drop out, giving the states which decide first a greater say in the electoral process.
The Republicans' final Iowa debate took place on Wednesday, with candidates largely refraining from attacking one another, opting instead to reiterate their positions on a host of issues from trade to taxes.
Opinion polls suggest that the Republican battle for Iowa is between Mitt Romney and Mike Huckabee, although former New York Mayor Rudy Giuliani continues to lead in national polls.
He has not campaigned heavily in Iowa, judging that he is unlikely to win over social conservatives who dominate the Republican electorate there.