Democratic presidential candidates from left, former Virginia Sen. Jim Webb, Sen. Bernie Sanders, of Vermont, Hillary Rodham Clinton, former Maryland Gov. Martin O’Malley, and former Rhode Island Gov. Lincoln Chafee take the stage before the CNN Democratic presidential debate Tuesday, Oct. 13, 2015, in Las Vegas.

The U.S. Democratic candidates for president clashed over foreign policy issues relating to Syria, ISIS and how to deal with Vladimir Putin’s Russia during the first primary debate for the party on Tuesday night.

Last week, Washington and its allies accused Moscow of targeting moderate U.S.-backed rebels in its strikes on Syria and that Russia was seeking to prop up President Bashar al-Assad’s regime.

Frontrunner in the 2016 presidential race and former Secretary of State Hillary Clinton said the U.S. – which is leading its own air war in Syria – should take on more of a lead role in the conflict.

“I think it’s important that the United States makes it very clear to Putin that it’s not acceptable for him to be in Syria creating more chaos, bombing people on behalf of Assad, and we can’t do that if we don’t take more of a leadership position, which is what I’m advocating,” Clinton said.

She also reaffirmed her support for creating a no-fly zone in Syria, saying Russia needed to be brought in as part of the solution to the conflict.

“I’m trying to figure out what leverage we have to get Russia to the table. You know, diplomacy is not about getting to the perfect solution. It’s about how you balance the risk,” she said.

Trailing just behind Clinton in the polls, Vermont senator and self-proclaimed socialist Bernie Sanders disagreed over the creation of a no-fly zone, describing the conflict in Syria as a “quagmire in a quagmire.”

In his pledge, Sanders said: “I will do everything that I can to make sure that the United States does not get involved in another quagmire like we did in Iraq, the worst foreign policy blunder in the history of this country.”

Iraq war and Clinton’s emails

Clinton had to defend her vote in favor of the Iraq war; a decision that perhaps still haunts her and may have hurt her chances during a 2008 presidential bid, when she ran against then senator Obama.

“Well, I recall very well being on a debate stage, I think, about 25 times with then Senator Obama, debating this very issue. After the election, he asked me to become Secretary of State. He valued my judgment.” Clinton said.

In perhaps an indirect criticism of Vice President Joe Biden, Clinton discussed her support for the raid that killed Osama Bin Laden, a move that Biden did not support.

Biden is presumed to be one of the few Democrats who can seriously challenge Clinton’s candidacy, but it’s unclear if he will join the race. The organizers of Tuesday’s debate invited Biden to join, but he reportedly declined to participate.

In a moment of agreement between the two biggest contenders, Senator Sanders defended Clinton against Republican accusations of wrong-doing after she used a private email server to conduct State Department business when she headed the department. “The American people are tired of hearing about your damn email,” Sanders said to a standing ovation.

Nuclear weapons

In response to a question on the “biggest threat to the United States,” Clinton responded that it was the threat from the spread of nuclear weapons.

“Nuclear material that can fall into the wrong hands. I know the terrorists are constantly seeking it, and that’s why we have to stay vigilant, but also united around the world to prevent that,” she added.

For Sanders, it was climate change. Jim Webb, a former senator, Marine, and Vietnam veteran with low ratings in the polls said it was the U.S.’s relationship with China, cyber warfare and the situation in the Middle East. Former Maryland governor Martin O’Malley argued it was Iran and ISIS.

The relatively friendly debate was in sharp contrast to the more raucous Republican debates in recent months, which featured many more candidates with bigger policy differences.

Clinton, who provided crisp, concise, carefully prepared answers was perhaps the most cautious when presenting issues that may be construed as controversial to independent voters. When asked whether she was a progressive or not she replied, “I’m a progressive, but a progressive who knows how to get things done.”

Democratic presidential candidates Sen. Bernie Sanders, of Vermont, left, and Hillary Rodham Clinton talk before the CNN Democratic presidential debate Tuesday, Oct. 13, 2015, in Las Vegas.

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