Democratic White House front-runner Elizabeth Warren has found herself under fierce attack from her rivals in a live television debate.
Contenders accused the Massachusetts senator of dodging a question on whether she would raise taxes.
Twelve White House hopefuls squared off in the primetime forum, with two other front-runners also under pressure.
Joe Biden has been battling Republican personal attacks, while Bernie Sanders is recovering from a heart attack.
Tuesday night’s debate, hosted by CNN and the New York Times, in the electoral battleground state of Ohio was the most crowded so far in the Democratic race.
Also on stage were South Bend, Indiana, mayor Pete Buttigieg, California Senator Kamala Harris, New York entrepreneur Andrew Yang, former Texas congressman Beto O’Rourke, Minnesota Senator Amy Klobuchar, New Jersey Senator Cory Booker, former Obama housing secretary Julian Castro, Hawaii congresswoman Tulsi Gabbard and billionaire activist Tom Steyer.
Languishing on single digits in the opinion polls, they strived to make a splash with time running out.
The Democratic White House race officially begins with the Iowa caucuses on 3 February.
The pack will be whittled down in state-by-state votes until a final candidate is crowned at the party convention next July, before he or she takes on President Donald Trump, a Republican, in the November 2020 election.
How did Warren find herself under attack?
Ms Warren was always expected to find a bullseye on her back on Tuesday night after accelerating to the tip of the field in the past two months.
Both Mr Sanders, a Vermont senator, and Ms Warren, a Massachusetts senator, favour an NHS-style system of free healthcare for Americans.
But unlike Mr Sanders, Ms Warren has repeatedly avoided stating explicitly whether her version of “Medicare for All” would raise taxes on working families.
She was pressed on the issue by debate moderators and replied that she would not sign any bill that raises costs on the middle class.
Standing beside Ms Warren, Mr Buttigieg rounded on her, saying: “You heard it tonight, a yes or no question that didn’t get a yes or no answer.
“This is why people here in the Midwest are so frustrated with Washington in general and Capitol Hill in particular.
“Your signature, senator, is to have a plan for everything except this – no plan has been laid out to explain how a multi-trillion dollar hole in this Medicare for All plan that Senator Warren is putting forward is supposed to get filled in.”
Even Ms Warren’s progressive ally Mr Sanders took a veiled jab, saying: “I do think it is appropriate to acknowledge that taxes will go up.”
Ms Klobuchar pounced: “At least Bernie’s being honest here and saying how he’s going to pay for this and taxes are going to go up.
“And I am sorry, Elizabeth, but you have not said that, and I think we owe it to the American people to tell them where we are going to send the invoice.”
Ms Klobuchar renewed her attack on Ms Warren over her proposed wealth tax to target income inequality.
“I want give a reality check here to Elizabeth,” said the Minnesotan. “No one on this stage wants to protect billionaires, not even the billionaire wants to protect billionaires,” she added, referring to Mr Steyer.
“We just have different approaches, your idea is not the only idea,” Ms Klobuchar told Ms Warren.
Ms Warren counter-punched: “I think as Democrats we are going to succeed when we dream big and fight hard, not when we dream small and quit before we get started.”
What did the candidates say about impeachment?
It was the first debate since congressional Democrats launched an impeachment inquiry into Mr Trump’s efforts to pressure Ukraine to investigate Joe Biden.
The first question of the night was about the congressional investigation that could attempt to remove the president from office.
In a show of unity, all candidates voiced support for the inquiry, railing against Mr Trump’s “criminality” and “corruption”.
What about the Hunter Biden story?
Mr Biden was asked about Mr Trump’s unsubstantiated claims that the former US vice-president improperly tried to aid his son Hunter Biden’s business interests in Ukraine.
“My son did nothing wrong,” replied Mr Biden, who is trying to steady his campaign after seeing his once commanding lead in opinion polls erode. “I did nothing wrong.”
“He [Mr Trump] doesn’t want me to be the candidate. He’s going after me because he knows that if I get the nomination I will beat him like a drum.”
He was pressed by the debate moderator on whether he made a mistake while he was the Obama administration’s point man on Ukraine by allowing his son to serve on the board of a Ukrainian gas company.
Mr Biden replied: “I never discussed a single thing with my son about anything having to do with Ukraine, no one has indicated I have. We’ve always kept everything separate.”
His Democratic rivals refrained from attacking Mr Biden on the issue.
How is Sanders faring?
Mr Sanders is being closely watched in the three-hour debate for signs of flagging stamina after suffering a heart attack earlier this month.
The oldest contender at 78, Mr Sanders has dropped into third place in the polls.
The self-described democratic socialist has so far delivered a steady performance.
He has been railing against billionaires and promising everyone would be guaranteed a job under his administration.
How did the candidates clash on Syria?
Democratic divisions between the hawkish and dovish wings of the party were once again on display.
In a comment that will likely elicit further scrutiny, Ms Warren said: “I think we ought to get out of the Middle East.
“I don’t think we should have troops in the Middle East.”
Ms Gabbard, often described as an isolationist, said: “Trump has the blood of the Kurds on his hands, but so do other politicians on both sides who have supported this regime-change war.”
The Hawaii congresswoman also blamed the “mainstream media” for being pro-war.
Mr Biden hit back: “That has not been the policy, to change the [Syrian] regime – it’s been to make sure the regime did not wipe out hundreds of thousands of innocent people!”
Mr Buttigieg also attacked Ms Gabbard, calling her “dead wrong”.
He added: “When we think our only choices are between endless war or total isolation the consequence is the disappearance of US leadership from the world stage.”
While the candidates disagreed on US intervention overseas, they united in pillorying Mr Trump’s policy on Syria.
Ms Harris said the president has “basically given 10,000 ISIS fighters a get-out-of-jail free card.”
She added: “That’s why ‘dude gotta go’ and when I am commander-in-chief we will stop this madness.”
How did the candidates spar on gun control?
In one of the sharpest exchanges of the night, Mr Buttigieg and Mr O’Rourke clashed over US firearms deaths.
Mr O’Rourke was challenged on his plan to remove assault-style weapons from private ownership under a so-called mandatory gun buyback.
A debate moderator pressed Mr O’Rourke: “Exactly how are you going to take away weapons from people who do not want to give them up and you don’t know where they are?”
Mr O’Rourke replied: “The expectation is that Americans will follow the law. I believe in this country, I believe in my fellow Americans, I believe they will do the right thing.
Mr Buttigieg said to Mr O’Rourke: “Look, congressman, you just made it clear you don’t know how this is actually going to take weapons off the streets.”
Mr O’Rourke implied that Mr Buttigieg was being “limited by the polls and the consultants and the focus groups”.
Mr Buttigieg hit back: “I don’t need lessons from you on courage, political or personal.”
Mr O’Rourke countered that it was “slap in the face” to victims of gun violence when Mr Buttigieg disparaged Mr O’Rourke’s policy as “a shiny object”.
Who will take on Trump in 2020?
Election day is still more than a year away but the race to become the Democratic challenger to Mr Trump is already well under way.
Joe Biden and Bernie Sanders have thrown their hats into the ring, but most of the other candidates are relatively unknown outside the Washington DC bubble.