Hillary Clinton and Bernie Sanders clash in bad-tempered Democratic debate
Hillary Clinton and Bernie Sanders have tangled aggressively in a Democratic presidential debate over trade and Wall Street influence.
Ms Clinton accused her opponent of turning his back on the car industry while Mr Sanders countered that her friends on Wall Street had "destroyed this economy".
It was a marked change in tone for the two Democrats, signalling his increasingly difficult task of slowing the party's front-runner. The candidates frequently interrupted one another and accused each other of misrepresenting their records.
"Let's have some facts instead of some rhetoric for a change," Ms Clinton snapped at Mr Sanders at one point.
"Let me tell my story, you tell yours," he shot back at another. "Your story is voting for every disastrous trade amendment and voting for corporate America."
More than once, he chafed at Ms Clinton's interruptions, saying: "Excuse me, I'm talking" or "Let me finish, please."
The debate in Flint, Michigan, came after Mr Sanders won three out of the four states contested over the weekend in the race for the Democratic nomination, although he barely made a dent in Ms Clinton's big delegate lead.
He won caucuses in Maine, Kansas and Nebraska, but Ms Clinton's victory in the Louisiana primary cancelled out his gains.
Their disagreements were clear, but the debate's tone was nothing like that of the Republican debate in Detroit three days earlier, a four-way face-off marked by a steady stream of personal attacks, insults and even sexual innuendo.
Ms Clinton said that while she and Mr Sanders have differences on policy, "compare the substance of this debate with what you saw on the Republican stage last week".
He chimed in: "We are, if elected president, going to invest a lot of money into mental health and when you watch these Republican debates you know why."
Each made a case for being the best candidate to defeat Republican front-runner Donald Trump in a November match-up.
Ms Clinton said she had won more votes than Mr Trump in the primaries, and predicted that his "bigotry, his bullying, his bluster are not going to wear well on the American people".
Mr Sanders said: "I would love to run against Donald Trump," adding that polls show "Sanders vs Trump does a lot better than Clinton vs Trump".
He also took direct aim at the former secretary of state's paid speeches to Wall Street banks and other financial companies.
Earlier, Mr Trump said he would push to change laws that prohibit waterboarding and other enhanced interrogation methods, arguing that banning them puts the US at a strategic disadvantage against Islamic State.
"We have to play the game the way they're playing the game," Mr Trump said in an interview on CBS's Face The Nation, the day after he told an audience in Florida that he would fight to expand the laws that regulate interrogation.
"I would like to strengthen the laws so that we can better compete."
His comments come as the US continues its uphill battle against IS militants across the Middle East. Mr Trump has repeatedly pointed to the tactics used by the group, including public beheadings and drownings in locked cages, as evidence that the US needs to dramatically escalate the tactics it uses.
Pressed on why he believed waterboarding had been banned, Mr Trump said: "Because I think we're weak - I think we've become very weak and ineffective. I think that's why we're not beating Isis. It's that mentality."
"Isn't that what separates us from the savages?" the programme's host John Dickerson asked.
"No, I don't think so," answered Mr Trump. "No, we have to beat the savages."
"We have to play the game the way they're playing the game. You're not going to win if we're soft and ... they have no rules," he said.
Mr Trump was speaking as Marco Rubio won Puerto Rico's Republican presidential primary election, with supporters saying he would help lift the island out of its long economic slump.
"The numbers are overwhelming," said Jenniffer Gonzalez, chairwoman of Puerto Rico's Republican Party. "This primary in Puerto Rico ... will demonstrate that the Hispanic vote is important."
That result came after Ted Cruz and Mr Trump each captured two victories in a four-state round of voting in the Republican race for the White House.
Mr Cruz, a Texas senator, claimed Kansas and Maine, and declared it "a manifestation of a real shift in momentum".
Mr Trump took Louisiana and Kentucky.