Democratic presidential candidate Hillary Clinton received surprise support from her chief rival Bernie Sanders for her use of a private email server as secretary of state during the party’s first televised debate of the campaign.
Mrs Clinton said her decision not to use a government email address was a mistake, and emphasised that she wanted to focus on policy issues that were more important to voters.
Mr Sanders unexpectedly came to her aid.
“Let me say something that may not be great politics, but I think the secretary is right,” he said.
“The American people are sick and tired of hearing about your damn emails.”
The crowd cheered and Mrs Clinton smiled.
“Thank you, Bernie,” she said, beaming broadly and shaking hands warmly with the senator from Vermont amid enthusiastic applause.
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The warm exchange was in contrast to earlier clashes between the two candidates over capitalism, gun control and US policy on Syria.
Five presidential hopefuls took part in Tuesday night’s debate in Las Vegas, Nevada.
One of them, former Rhode Island governor Lincoln Chafee, who has criticised Mrs Clinton over the emails, said it was important that the next president adhere to the best in ethical standards.
Asked by the moderator if she wanted to respond, Mrs Clinton answered, to applause, with one word: “No.”
The former first lady, who is trying to check Mr Sanders’ momentum, attacked him for saying the US should model its economy on European countries such as Denmark, Sweden and Norway.
“I think what Senator Sanders is saying certainly makes sense in the terms of the inequality that we have,” she said.
“But we are not Denmark. I love Denmark. We’re the United States of America.”
Mr Sanders, a self-described “democratic socialist”, said he did not subscribe to the capitalist system.
“Do I consider myself part of the casino capitalist process by which so few have so much and so many have so little, by which Wall Street’s greed and recklessness wrecked this economy? No, I don’t,” he said.
The senator is polling ahead of Mrs Clinton in New Hampshire, and is attracting large crowds at campaign events across the country.
The pair also clashed over gun violence, an issue that has shot up the agenda after repeated schools shootings.
Mrs Clinton said her opponent had not been tough enough on the issue and said he had voted against a provision that would have opened gun manufacturers up to more scrutiny.
Mr Sanders has lobbied for what he calls a sensible approach on gun control, and voted against the 1993 Brady handgun bill signed into law by President Bill Clinton.
Asked to defend that position, Mr Sanders said he backed the expansion of background checks for people wanting to purchase guns and to get rid of gaps in the law that make it easier to sell and buy guns at gun shows.
Mrs Clinton and Mr Sanders were joined on stage by Chafee, former Maryland governor Martin O’Malley and ex-senator James Webb of Virginia in the first of six scheduled debates in the race to take on the Republican nominee for the White House in 2016.