Fact check: Are seven children and teens killed by guns a day?

Warren said this one, and it's almost dead on, according to data published in the New England Journal of Medicine. The study found that as many as eight children are killed by guns each day.

Castro calls O'Rourke 'misinformed' on immigration after debate

In the post-debate spin room, Castro again said O'Rourke has not done his homework on immigration, calling him "misinformed."

"I don't think he's done his homework," Castro said. "The difference between my immigration plan and his immigration plan is an important one. The only way we're going to end family separations ... is treat [crossing the border] as a civil violation."

He also said that other lawmakers had a better grasp of the issue.

"I do find it somewhat ironic that a senator from Massachusetts and a senator from New Jersey and a congressman from Ohio have a better understanding of immigration law than Congressman O'Rourke," he said.

Booker's side-eye gets traction on Twitter

The memes are rolling in and the image of the night has to be Booker giving O'Rourke a bit of side-eye early in the debate.

Chris Matthews asked Booker about the moment, and the candidate said that when he heard O'Rourke offer some of his answer in Spanish: "He threw down the gauntlet and I had to respond."

Based on a casual observation of Twitter, Beto appears to be the most-snarked-about candidate of the evening, with the Booker moment offering a chance for a variety of cultural references.

And O’Rourke went back to his Spanish quite a few times — a strategy that was not lost on much of the snarkier Twitter contingent.

Trump campaign: Dem debate like 'an in-kind contribution'

The review from the Trump campaign is in: “This debate was the best argument for President Trump’s re-election and should really be counted as an in-kind contribution to the President’s campaign. The Democrats proposed a radical government takeover of American society that would demolish the American dream so many are gaining access to under the growing Trump economy."

Klobuchar says she can win in Trump country

Klobuchar touted her experience and winning in Trump country: In the post-debate spin room, the Minnesota lawmaker said this election has to be a "national mandate" on climate change, health care and immigration, among other issues, and that she's the one to get it done.

"Every time I lead our ticket in Minnesota we win big," she told MSNBC's Chris Matthews. "I have won in districts, including ones that Trump won, by 20 points." 

Ryan says Democrats must drop 'Ivy League' politics to win

In the post-debate spin room, Ohio Rep. Tim Ryan once again called on Democrats to abandon what he characterized as coastal elitism and pay more attention to the economic hardships of working class families in the Rust Belt.

Ryan, as he did during the debate, told MSNBC's Chris Matthews that focusing on pocketbook issues in the industrial Midwest and dropping "Ivy League" cultural politics would help Democrats retake the White House.

Booker says he wouldn't accept a veep offer from a male presidential candidate

Cory Booker said he would not accept a vice president offer from Joe Biden — or any other male presidential candidate, for that matter.

In the MSNBC spin room, the New Jersey senator told Chris Matthews that he does not want to see a single-gender presidential ticket, adding that he believes a woman and person of color should be on the Democratic ballot.

Social media complicates the views of who won the night

One of the challenges for both those debating on stage and reporters monitoring the debate is the always looming question of who won. A consensus answer might be more difficult this evening because of the unquestionable effect of social media.

While many political reporters working for major media organizations maintain an active presence on Twitter, the social media network features a far more diverse cast of influential figures and thought leaders than the nation’s newsrooms. That difference between journalists and the Twitterati might ultimately shape assessments of who emerged the victor in tonight’s debate.

Castro says O'Rourke didn't do his 'homework'

Fact check: What is Section 1325, and why do Castro and O'Rourke disagree about it?

Julián Castro made the claim earlier this evening that the reason the Trump administration is separating families is because "they are using section 1325 of that act which criminalizes coming across the border to incarcerate the parents and then separate them."

This is true. Section 1325 within the U.S. Code, “sets forth criminal offenses relating to (1) improper entry into the United States by an alien." The Trump administration has used this statute to prosecute, and detain, people for illegally crossing the U.S. border. 

Castro, referring to himself, also said that, “Some of us on this stage have called to end that section, to terminate it."

"Some like Congressman O’Rourke have not," Castro said. 

O’Rourke, in fact, told CNN earlier this month that he did “not think it should be repealed,” citing attempts by some crossing the border to smuggle people or drugs into the U.S. 

Top candidate Google searches

Castro trends on family origins

Observation: Castro and de Blasio demonstrated different skill levels in the bringing of personal biography to the debate stage tonight. De Blasio described his experience raising a black son and his father’s mental and physical injuries in World War II. Castro spoke of his family’s origins in Mexico and climb into public service in the United States. At the end of the evening, Castro had been the subject of 147,000 tweets, making him a trending topic.