The gloves came off in New Hampshire on Friday night as Democratic presidential candidates sparred in a fiery debate after another dramatic week in U.S. politics.

Seven candidates for the Democratic nomination took to the stage in Manchester days after Donald Trump gave the State of the Union address, was acquitted at a Senate impeachment trial and the Iowa caucuses descended into chaos.

The surprise ticket in Iowa was former South Bend Indiana mayor Pete Buttigieg, who looks to have finished in a near-tie at the top with Bernie Sanders. Heading into Tuesday's New Hampshire primary the 38-year-old was on the front foot – and the focus of repeated attacks – in the debate.

Senator Amy Klobuchar had another good debate night and billionaire Tom Steyer stood out, but former Vice President Joe Biden struggled while Senator Elizabeth Warren and entrepreneur Andrew Yang had quiet evenings.

Buttigieg the post-Iowa target

Buttigieg was always likely to be in the crosshairs after exceeding expectations in Iowa, and laid his own marker down early by taking pre-emptive shots at Sanders and national polling frontrunner Biden.

He argued the biggest risk for the Democrats going into the 2020 election was "trying to fall back on the familiar" – a sleight at Biden – or a politics that says "my way or the highway" – a reference to Sanders.

"We cannot solve the problems before us by looking back," Buttigieg warned, drawing Biden to respond "I don't know what about the past of Barack Obama and Joe Biden was so bad."

Buttigieg received applause from the crowd in New Hampshire – where the opioid crisis has hit hard – for his pledge to end incarceration as a solution to drug abuse and though he has a smaller operation in the state than in Iowa, polls suggest he has climbed to within touching distance of leader Sanders.

The latest tracker from WBZ/Boston Globe/Suffolk University, released minutes after the debate, put Buttigieg on 25 percent and Sanders on 24 with Warren and Biden trailing on 14 and 11 respectively. 

Buttigieg focused relentlessly on the future and achievable change, but was also repeatedly criticized over big money fundraising as well as a lack of experience.

The military veteran, who has struggled to win support from non-white voters to-date, also faltered on a question about the increased rate of African-American arrests during his eight years as mayor in South Bend. 

New Hampshire is key to maintaining his campaign's momentum and demonstrating electability heading into contests in Nevada and South Carolina.

Klobuchar came in fifth in Iowa but received more support than expected, and New Hampshire is probably her last chance to make an impact if she is to stay in the race.

She again delivered a strong debate performance focused on her electability but peppered with sharp criticisms of "newcomer" Buttigieg and "divisive" Sanders. 

Her problem in the campaign so far has been translating good showings on stage into high ratings in the polls – with just four days before the primary, she will hope this time she can make a breakthrough.

Sanders sticks to the script

Sanders beat Hillary Clinton by over 20 points in the 2016 New Hampshire primary, and though such a large scale of victory is unlikely in the multi-horse 2020 race he is ahead in most polls in the state and has also announced a 25 million U.S. dollar fundraising haul for January.

The 77-year-old took hits from moderates including Klobuchar, who warned that Democrats "are not going to be able to out-divide the divider in chief" but stuck to a script that proved popular in New Hampshire four years ago. 

He reserved his strongest attacks for rival Buttigieg on fundraising, saying "if we want to change America, you're not going to do it by electing candidates who are going out to rich people's homes, begging for money."

Biden took the fight to Sanders, notably on guns and on healthcare. Sanders is vulnerable among Democrats on gun rights: he has previously opposed expanded background checks, but insists his views have changed.

The former vice president had a terrible night in Iowa – a "gut punch" in his own words – and polls suggest he should prepare for another blow in New Hampshire.

The former vice president's edge is his popularity with non-white voters, and a central part of his mission on Friday was retaining support in later voting states with references to his past achievements and experience.

He made the argument that a Biden presidency would be a continuation of the Obama years, and stressed his role in major diplomatic achievements including the Iran nuclear deal and the Paris climate agreement.

Warren, not long ago on Biden's tail, is now seeking to get back in the game with a call for unity. She once again delivered a solid performance and took aim at Buttigieg, but received comparatively little speaking time.

Steyer, the long shot billionaire candidate, stood out as a disruptor – making repeated pitches to African American voters and criticizing each of the other candidates.

Yang, the entrepreneur who failed to qualify for the last debate, returned to emphasizing his universal basic income plan after a poor showing in Iowa but struggled to make an impact.