Democratic presidential candidate Hillary Clinton gives a thumbs up to supporters at the end of the first official Democratic candidates debate of the 2016 presidential campaign in Las Vegas, Nevada October 13, 2015. [Photo/Agencies]

LAS VEGAS - With a smile and a handshake, Democratic presidential candidate Hillary Clinton secured unexpected support from chief rival Bernie Sanders over an email scandal during their first debate, helping to defuse an issue that has dogged her campaign.

Sanders, a 74-year-old U.S. senator from Vermont came to her rescue on Tuesday night as Clinton, 67, said she wanted to focus on more pressing policy issues when questioned about a private email server she used as U.S. secretary of state.

"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."

"Thank you. Me too. Me too," a beaming Clinton responded shortly before turning to shake the hand of a smiling Sanders while the crowd roared.

Shortly after that moment of warmth, however, Clinton and Sanders clashed over their views about Wall Street, capitalism, gun control, and U.S. policy on Syria in a surprisingly feisty first debate between candidates who have largely steered clear of criticizing each other on the campaign trail.

Clinton, who has seen her lead over Sanders narrow during the email controversy, delivered a smooth performance that could solidify her status as front-runner and raise questions about the viability of a possible candidacy by Vice President Joe Biden.

Trying to stem Sanders' momentum and calm the worries of some supporters about her slide in opinion polls, she aggressively drew sharp contrasts with the self-described democratic socialist.

Clinton criticized his remark in the debate that the United States should model its economy after 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. But we are not Denmark," said Clinton, who described herself as a progressive but "a progressive who likes to get things done."

Sanders 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.

Sanders also knocked the administration of President Bill Clinton, the front-runner's husband, for its deregulation of Wall Street in the 1990s.

"Congress does not regulate Wall Street. Wall Street regulates Congress," Sanders said critically.

Clinton said the United States needed to do more than focus its fire on big banks.

"We have work to do. You'll get no argument from me. But I know if we don't come in with a very tough and comprehensive approach, like the plan I'm recommending, we're going to be behind instead of ahead," she said.

CLASH OVER GUN CONTROL

The two candidates also clashed over gun violence, an increasingly potent issue after repeated school shootings across the country. Clinton said Sanders had not been tough enough on the issue, noting he voted for a provision to free gun manufacturers from legal accountability.

"I voted against it. I was in the Senate at the same time. It wasn't that complicated to me," she said. "We need to stand up and say enough of that. We're not going to let it continue."

Sanders, noting he represents a rural state where many people own guns, said he supported the expansion of background checks for people wanting to buy guns and to scrap gaps in the law that make it easier to sell and buy guns at gun shows.

The two leading candidates were joined by former Rhode Island Governor Lincoln Chafee, former Maryland Governor Martin O'Malley and former U.S. Senator James Webb of Virginia in the first of six scheduled debates in the race to be the party's nominee in the November 2016 presidential election.

The lesser known candidates made veiled attacks on Clinton. Chafee noted he had "no scandals" during his political career; Webb said he was not co-opted by the political system.

Sanders' "damn emails" statement was the top social moment of the two-hour debate on Facebook and Sanders himself was the candidate most discussed on the social media network, according to Andy Stone, a spokesman for Facebook.

Clinton has said her email server in her New York State home was used for convenience and not to skirt transparency laws. The Federal Bureau of Investigation has taken the server and other computer hardware to determine whether sensitive government information was mishandled in Clinton's email correspondence.

Chafee, who has been critical of Clinton in the context of 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, Clinton answered, to applause, with one word: "No."

Biden, who is considering launching a run for the nomination, was not on the stage but loomed in the background. Clinton took a veiled shot at Biden by emphasizing her involvement in President Barack Obama's decision to authorize the raid that killed former al Qaeda leader Osama bin Laden.

Clinton was in favor of the raid. Biden advised against it.

Late in the debate, the candidates were asked which enemy they were most proud of making.

"Well, in addition to the NRA (National Rifle Association), the health insurance companies, the drug companies, the Iranians, probably the Republicans," Clinton said to laughter from the audience.