CNN/Des Moines Register Iowa Debate

Six of the Democratic presidential candidates are meeting for a debate in Iowa Tuesday night at a time of escalating tension between Vermont Sen. Bernie Sanders and Massachusetts Sen. Elizabeth Warren, the leading two progressive candidates who had tried until now to avoid attacking one another.

(CNN) -- Tuesday marked the last Democratic presidential debate before the voting begins with the Iowa caucuses on February 3. The debate aired on CNN, and the network provided fact check coverage of the debate as it aired.

The debate was hosted by CNN and the Des Moines Register at Drake University in Des Moines, Iowa. It included six candidates who met the party's qualification criteria, the smallest number to date.

The candidates were former Vice President Joe Biden; Vermont Sen. Bernie Sanders; Massachusetts Sen. Elizabeth Warren; former South Bend, Indiana, Mayor Pete Buttigieg; Minnesota Sen. Amy Klobuchar; and businessman Tom Steyer.

Buttigieg on Trump administration admitting Iran deal worked

Former Mayor Pete Buttigieg asserted during the debate on Tuesday that the Trump administration admitted that the Iran nuclear deal was working before pulling out of it.

Buttigieg said, "By gutting the Iran nuclear deal, one that, by the way, the Trump administration itself admitted was working, certified that it was preventing progress toward a nuclear Iran, by gutting that, they have made the region more dangerous and set off the chain of events that we are now dealing with as it escalates even closer to the brink of outright war."

Facts First: This is basically true. By repeatedly recertifying the nuclear deal and waiving sanctions against Tehran as a result, the Trump administration effectively acknowledged that Iran was abiding by the terms of the deal even as the President publicly criticized it.

The terms of the nuclear deal required the US president to reauthorize it every 120 days to keep sanctions from kicking in. Trump didn't leave the deal until May 2018 and reauthorized it a handful of times after taking office.

CNN previously reported that the President promised to kill the deal on the campaign trail but was persuaded by cabinet members and allies several times to recertify Iran's compliance. Former Defense Secretary James Mattis told the Senate Armed Services committee in April 2018 that the verification provisions in the pact were "pretty robust" though he did not publicly back the deal. Despite his criticism of the deal, neither Trump nor his aides had been able to say that Iran was violating the terms of the agreement.

- Caroline Kelly and Zachary Cohen

Sanders on cost of NAFTA and permanent normal trade relations with China

Sanders repeated his claim that NAFTA and permanent normal trade relations with China have cost the US "some 4 million jobs."

"I am sick and tired," said Sanders as he drew a contrast with former Vice President Joe Biden, pointing to large multinational corporations that he says have reaped the benefits.

Facts First: This is likely an overestimate of the impact trade agreements can have on the country's employment.

It's difficult to measure the overall economic impact of the North American Free Trade Agreement since trade and investment trends can be affected by a number of factors, including economic growth, inflation and even a weakening dollar, according to the Congressional Research Service.

Most estimates find that NAFTA had little if any impact on national employment levels, though the effect was uneven across regions and industries.

The left-leaning Economic Policy Institute found that between 1993 and 2013, the US trade deficit with Mexico and Canada increased from $17 billion to $177.2 billion and displaced 851,700 US jobs.

By contrast, the entry of China into the World Trade Organization in 2001 likely had a much larger impact because of sudden competition from cheaper imports. But even the high end of job loss estimates from EPI found that the change in trade status for China caused a loss of 3.4 million jobs between 2001 and 2017.

Another estimate, from a 2016 study by economists at the Massachusetts Institute of Technology, found that normalizing trade relations with China cost the US between 2 million and 2.4 million jobs between 1999 and 2011.

- Donna Borak

Biden on Iraq War stance

Biden repeated his false claim that he opposed the war in Iraq from the moment the war began.

Biden said he made a "mistake" in casting a 2002 vote, as a senator from Delaware, to give President George W. Bush the authority to go to war in Iraq. But he said he cast the vote because the Bush administration had said "they were just going to get inspectors" into Iraq to check for weapons of mass destruction -- and that, once Bush actually went to war, he became immediately opposed: "From that point on, I was in the position of making the case that it was a big, big mistake."

Facts First: As fact checkers have repeatedly noted, Biden did not oppose the war in Iraq from the point it started in March 2003. He did begin calling his 2002 vote a "mistake" in 2005, two years into the war, but he was a vocal public supporter of the war in 2003 and 2004. And he made clear in 2002 and 2003, both before and after the war started, that he had known he was voting to authorize a possible war, not only to try to get inspectors into Iraq.

CNN's Facts First team has debunked various versions of Biden's claim that he opposed the war from the moment it started. Read longer articles on that here, here and here.

Here are a few representative Biden quotes. In a February 2003 speech in Delaware, he said, "Let everyone here be absolutely clear: I supported the resolution to go to war. I am NOT opposed to war to remove weapons of mass destruction from Iraq. I am NOT opposed to war to remove Saddam from those weapons if it comes to that."

It's true that Biden criticized Bush's approach to diplomacy in the lead-up to the war, warned in the lead-up to the war that Bush was not being honest about how hard the war would be, and he criticized Bush's handling of the war from its first weeks on. But Biden made clear that he supported the war despite that criticism.

In a July 2003 speech at the Brookings Institution, Biden said: "Nine months ago, I voted with my colleagues to give the president of the United States of America the authority to use force and I would vote that way again today. It was the right vote then and would be a correct vote today."

During the debate on Tuesday, Biden also offered a confusing timeline of his positions on the war, saying, "I said 13 years ago it was a mistake to give the president the authority to go to war if, in fact, he couldn't get inspectors into Iraq to stop -- what thought to be -- the attempt to get a nuclear weapon. It was a mistake. And I acknowledged that."

When Biden said "13 years ago," he appeared to be referring to how, in 2006 and 2007, he was calling his 2002 vote a mistake. The vote itself was more than 17 years ago.

- Daniel Dale and Nate McDermott

Biden on threat to US embassies

Biden said that President Donald Trump "flat-out lied" when he claimed the US killed Iran's top military general because he was targeting four US embassies.

"Quite frankly, I think he's flat-out lied about saying that the reason he went after -- the reason he made the strike was because our embassies were about to be bombed," Biden said.

Facts First: Trump has yet to provide evidence backing up his claim that Iranian Gen. Qasem Soleimani was actively planning new attacks against four US embassies and top administration officials have struggled to defend the President's comments. But there is no way to know if Trump "flat-out lied" without seeing the underlying intelligence, which remains classified.

Trump claimed at an Ohio rally last week that Soleimani "was actively planning new attacks." He later told Fox News, "I believe it probably would've been four embassies," naming Baghdad as one.

Senior administration officials have repeatedly pointed to danger facing US embassies in the Middle East.

Defense Secretary Mark Esper said this past weekend he "didn't see" a specific threat against four embassies in the intelligence.

"What the President said with regard to the four embassies is what I believe as well. He said that he believed that they probably, that they could have been targeting the embassies in the region," Esper added.

Similarly, Trump's national security adviser Robert O'Brien said in an interview on Sunday with ABC's "This Week" that it was unclear whether embassies or US military bases would be targeted, but insisted Trump's claim about four embassies being threatened was "consistent with the intelligence."

Citing two State Department officials, CNN reported on Monday that State Department officials involved in US embassy security were not made aware of imminent threats to four specific US embassies and didn't issue warnings about specific dangers to any US embassy before the administration targeted Soleimani.

The State Department sent a global warning to all US embassies before the strike occurred, a senior State Department official said and the department spokesperson confirmed, but it was not directed at specific embassies and did not warn of an imminent attack.

- Zachary Cohen