Final #DemDebate before New Hampshire’s first in the nation primary held in Manchester
CNN debate (screengrab)

Democratic presidential candidates will spar on the debate stage Friday as Bernie Sanders and Pete Buttigieg seek to build on their robust performances in the Iowa caucuses and Joe Biden looks to rebound from his dismal showing.

Both Sanders, the leftist senator from Vermont, and Buttigieg, the former mayor of South Bend, Indiana, claimed victory in the chaotic Iowa caucuses and the pair are neck-and-neck in the polls ahead of the next contest in New Hampshire.

The Granite State holds a primary on Tuesday as the Democratic Party seeks to narrow down the crowded field and come up with an opponent to defeat President Donald Trump in November.

Seven Democratic candidates will take part in Friday night's televised three-hour debate at Saint Anselm College in Manchester, New Hampshire, which begins at 8:00 pm (0100 GMT).

Besides Buttigieg, Sanders and Biden, Massachusetts Senator Elizabeth Warren, Minnesota Senator Amy Klobuchar, businessman Tom Steyer and entrepreneur Andrew Yang will be on the stage.

While Buttigieg, 38, and Sanders, 78, are seeking to capitalize on the momentum from Iowa, Biden is looking to bounce back from his performance in the Midwestern farm state.

The latest New Hampshire poll spells trouble, however, for the 77-year-old Biden, who finished fourth in Iowa.

The Boston Globe/WBZ-TV/Suffolk University poll had Sanders, who won New Hampshire four years ago before losing the nomination to Hillary Clinton, topping the field with 24 percent.

Buttigieg was next at 23 percent, up from 11 percent on Monday, while Biden saw his support fall to 11 percent from 18 percent over the same time period.

'A lot on the line'

"Buttigieg has actually been strong in this state since the summer, and it's really been overlooked," said Neil Levesque, executive director at the New Hampshire Institute of Politics at Saint Anselm College.

Biden is expected to use the debate to step up attacks on his rivals -- Buttigieg for his relative lack of experience and Sanders for his self-described democratic socialist label.

Biden will have "a lot on the line," Levesque told AFP.

"He's really got to perform and he's got to show people and remind them that he believes he's the best candidate to go up against Donald Trump," he said.

Biden stayed off the campaign trail on Thursday to meet with his advisors and The New York Times reported on Friday that veteran Democratic strategist Anita Dunn would be taking on an expanded role in his campaign.

Sanders took aim at Buttigieg on Thursday, saying he had the most "billionaire donors of any Democrat" and Wall Street money was now eyeing him more closely after his performance in Iowa.

"I like Pete Buttigieg, nice guy," Sanders said. "But we are in a moment where billionaires control not only our economy but our political life."

Sanders also fired barbs at an actual billionaire -- Democratic candidate Michael Bloomberg -- who will not be on the debate stage but is looming large over the primaries.

The former New York mayor chose to ignore the early nominating contests and has spent heavily on advertising, hoping to make a splash on "Super Tuesday" on March 3, when 14 states hold primaries.

"He's entitled to run for president," Sanders said of Bloomberg. "No problem with that. Smart guy.

"But he is spending hundreds and hundreds of millions of dollars to buy the election. There is something wrong with that."

Walsh drops out

Addressing a military veterans group on Thursday, Buttigieg, who was deployed to Afghanistan as a US Navy intelligence officer, said his campaign had received "extraordinary validation" in Iowa.

"I'm also mindful and humbled by the fact that New Hampshire is not the kind of place to let Iowa or anybody else tell you what to do," the centrist candidate said.

Buttigieg and Sanders finished in a dead heat in Iowa and each claimed victory -- the former mayor based on the number of delegates who will be sent to the Democratic convention in July and the Vermont senator on the basis of the popular vote.

Iowa's complicated caucus system was marred by an embarrassing technical meltdown that affected the reporting of the returns and no winner has been declared amid a review of the results.

Former Illinois congressman Joe Walsh announced meanwhile that he was ending his quixotic effort to challenge Trump for the Republican nomination after being trounced in the party's own caucuses in Iowa.

Calling Trump unfit for office, the former conservative talk show host announced in August that he would challenge him for the nomination but he got only 1.1 percent of the vote in Iowa.

After New Hampshire, the candidates turn their sights on Nevada on February 22, South Carolina on February 29 and then Super Tuesday.