Six candidates took the stage in Las Vegas for the ninth debate of the primary season, hosted by NBC News, MSNBC, the Nevada Independent and Telemundo.

Five of the candidates, Bernie Sanders, Joe Biden, Elizabeth Warren, Pete Buttigieg and Amy Klobuchar, are old hat — but it's the first presidential debate for former New York Mayor Mike Bloomberg, who immediately came under fire.

We were fact-checking the Democratic debate in real time.

Buttigieg accuses Klobuchar of supporting Trump's judges. What's he talking about?

Buttigieg, the former mayor of South Bend, Indiana, claimed that Klobuchar, a senator from Minnesota, was the likeliest "of the senators running for president" to vote for judges appointed by President Donald Trump, drawing a complaint from Klobuchar that his numbers were wrong.

"I have opposed, not supported, two-thirds of the Trump judges, so get your numbers right, and I am in the top 10 to 15 of opposing them," Klobuchar said.

But Buttigieg didn't say she'd voted for Trump's judges two-thirds of the time. He said she'd voted for Trump's judges more than any other Democrat on the stage. And that's true.

Here's the fine print: The progressive blog ThinkProgress reported nearly a year ago that Klobuchar had voted for more than 56 percent of Trump's judicial nominees who were eventually confirmed — that may be where Klobuchar prepped her "two-thirds" response.

Her campaign told NBC News on Wednesday night that those numbers are outdated and that, using the same methodology, the senator has voted in favor of Trump's judicial nominees just 33.51 percent of the time. That's still more than her fellow senators Sanders and Warren, who voted for Trump's judicial nominees about 25 percent of the time by the same math.

Did Klobuchar vote to make English the national language?

Buttigieg laid into Klobuchar for supporting legislation to declare English the official language of the U.S.

"Do you know the message that sends in as multilingual a state as Nevada to immigrants?" he asked.

Klobuchar was one of 17 Democrats to support a 2007 amendment to end a requirement for federal agencies to provide materials in languages other than English, according to The Associated Press. She disavowed the stance last week, saying English shouldn't be the national language.

Bloomberg touts drop in crime rate under his watch

"When I got into office, there were 650 murders a year in New York City," Bloomberg said, defending his record on the "stop and frisk" policy the police pursued when he was mayor. "The crime rate did go from 650, 50 percent down, to 300. And we have to keep a lid on crime."

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

During his tenure, the murder rate in New York City — not the crime rate — dropped by roughly half, going from 649 murders in 2001 (his first year in office) to 335 in 2013 (his last year in office). But it's a stretch to attribute the decline to expanded use of the stop-and-frisk strategy. The murder rate had been declining for a decade before he took office, and it continued to decline after he left after three terms — suggesting that other forces were in play. The murder rate kept falling after Mayor Bill de Blasio formally ended the policy in 2014.

Studies have also struggled to find proof of a relationship between stop-and-frisk and a reduction in crime.

Download the NBC News app for breaking news and politics

Did Amazon pay $0 in federal income tax in 2018?

Buttigieg claimed that big companies like Amazon and Chevron paid nothing in federal income tax in 2018.

"What we've got to do is level the playing field, where a company like Amazon, Chevron, is paying literally zero on billions of dollars in profits, and it puts small businesses like the ones that are revitalizing my own city, often Latino-owned on our west side, at a disadvantage," he said.

That's true. Amazon paid $0 in federal income tax on more than $11 billion in profit before taxes in 2018. It also got a $129 million tax rebate from the federal government. Chevron also paid $0 in federal income tax, on more than $4.5 billion in income, in 2018. The company also got a federal tax rebate, to the tune of $181 million.

Amazon's and Chevron's low tax bills stem partly from the Trump administration's corporate tax cut from 35 percent to 21 percent in 2017. Many companies have a longstanding practice of using tax deferral, a tax instrument that lets businesses postpone paying taxes until a later year. Trump's decrease in the tax rate allowed companies to defer more taxes. Amazon's low tax bill also stemmed from tax credits for investments in research and development, stock-based employee compensation and so-called carryforward losses from years when the company didn't bring in profits.

Sanders says billionaires' wealth skyrocketed compared to average Americans'. Is he right?

"We have enormous problems facing this country, and we cannot continue seeing a situation where in the last three years, billionaires in this country saw an $850 billion increase in their wealth. Congratulations, Mr. Bloomberg. But the average American last year saw less than a 1 percent increase in his or her income. That's wrong," said Sanders, an independent senator from Vermont.

This is mostly true. Bloomberg's Billionaire Index reported in December that 172 American billionaires included in its ranking added $500 billion to their wealth in 2019. Bloomberg reported that the country's 173 biggest billionaires lost 5.9 percent of their total wealth in 2018, leaving them with $1.9 trillion at the end of the year. U.S. billionaires included in the index added $315 billion to their net worth in 2017. That amounts to $815 billion in total increases, not $850 billion.

Sanders' claim that "the average American saw less than a 1 percent increase in their income" is correct. The median household income increased by 0.9 percent from 2017 to 2018, according to the Census Bureau. Family household median income increased by 1.2 percent, while single household income increased by 2.4 percent.

Did Bloomberg oppose Obamacare in 2010?

"The mayor said, when we passed it, the signature piece of this administration, 'It's a disgrace.' They're the exact words. It was a disgrace. Look it up. Check it out. 'It was a disgrace,'" Biden said of Bloomberg's stance on the Affordable Care Act.

Biden's right. Bloomberg did call Obamacare a "disgrace" in 2010, and there's video — the former vice president just put it in an online ad. Bloomberg's health care plan, meanwhile, includes a proposal to "build on the ACA to achieve universal health coverage."

How much did the health care industry make?

"The health care industry made $100 billion in profits," Sanders claimed, making a push for his health insurance plan, Medicare for All.

"Somehow or another, Canada can provide universal health care to all their people," Sanders said. "U.K. can do it, France can do it, Germany could, all of Europe can do it. Gee whiz. Somehow or another, we are the only major country on Earth that can't do it. Why is that?"

In the context of health insurance, Sanders' characterization of profits is an exaggeration. The health insurance industry earned $23.4 billion in 2018, according to the National Association of Insurance Commissioners. The industry earned $16.1 billion in 2017.

However, a survey of some of the country's hospitals reported $91 billion of operating revenue in 2016, according to a 2017 Deloitte survey. Meanwhile, two of the world's biggest pharmaceutical companies — Pfizer and Roche — reported $12.69 billion and $14.1 billion respectively for fiscal year 2019.

Why did Bloomberg's administration cut back on stop-and-frisk?

Stop-and-frisk "got out of control. And when we discovered, I discovered, that we were doing many, many, too many stop-and-frisks, we cut 95 percent of it out," Bloomberg claimed Wednesday night.

That is both misleading and false. The New York Police Department's use of the strategy during his administration didn't happen without his awareness, and the practice was scaled back significantly thanks to a 2013 court order declaring it unconstitutional, not Bloomberg's change of heart.

In his three terms as mayor, Bloomberg expanded and championed stop-and-frisk — the strategy that gave police the authority to detain people suspected of committing a crime and led to a practice of stopping mostly black and Hispanic men — right up until days before he announced that he was running for president, according to a comprehensive timeline reported by The New York Times.

Is Bloomberg against raising the minimum wage?

Sanders, in a veiled shot at Bloomberg, suggested: "Maybe we can talk about a billionaire saying that we should not raise the minimum wage. Or that we should cut Social Security, Medicare, Medicaid. If that's a way to beat Donald Trump, wow! I would be very surprised."

Bloomberg said in a 2015 interview with his own Bloomberg channel that he had "never" been in favor of raising the minimum wage. But now, as a presidential candidate, he backs raising the minimum wage to $15, according his campaign website.