"You just said that two minutes ago," Castro said to Biden, accusing him of flip-flopping and picking and choosing when to say he supported President Obama.
"I stand with Barack Obama all eight years," Biden said. "Good, bad, and indifferent."
Before the debate began, Republicans made their voice heard, renting a plane to tow a giant banner over the campus of Texas State University.
Here is a look at the ten candidates in Thursday's debate:
1. Still the front runner, Joe Biden. For a third consecutive debate, former Vice President Biden faced a series of attacks from other Democrats, and probably had his strongest debate yet. Yes, he had some mini verbal stumbles, talking about a record player at one point - and working himself into some verbal cul-de-sacs - but Biden was much more on point and definitive as he questioned the cost of the Medicare For All health plan favored by Bernie Sanders and Elizabeth Warren. Biden finished on a very personal note, talking about the tragedy he has faced in his family life.
2. Elizabeth Warren keeps chugging along. While there was a lot of talk about Biden and Warren being on the debate stage for the first time together, there wasn't much to talk about from the debate. Yes, they sparred a bit over the details of Medicare For All, and Biden threw some weak elbows on other policy points - but for the most part, the two avoided any policy showdowns. After three debates, it's obvious that Warren is in the top tier with Biden, as she has been able to create a lot of organic support for her candidacy, with a stump speech that's well oiled, and position papers for just about everything a voter could imagine. The strategy question for coming weeks is a simple one for Warren. Does she take the fight directly to Biden on the campaign trail? Or does she stick with the issues and policy matters which have driven her approach so far.
3. Sanders tries to puncture focus on Biden-Warren. As Warren has made her move up in the polls, the Sanders camp has expressed aggravation with the press coverage, basically arguing that Sanders is being left out. he's been getting - or maybe in the mind of campaign officials, not getting - from the news media. Usually people associate complaints about the press with Republicans - but Sanders has always had a somewhat rumpled relationship with the news media. "Bernie Sanders thinks media is unfair, so he created his own," read one AP headline. "Sanders team frustrated with media coverage," was another. "Bernie Sanders Is As Frustrated as Ever With Corporate Media," the Nation wrote. Sanders can hold his own on any issue - but does that get him to the nomination?
4. Kamala Harris looks for lasting gains. All three debates for Democrats have both included solid moments and exchanges for Kamala Harris. After taking on Joe Biden over his past actions regarding civil rights in the first debate, and going aggressive last month, this time Harris played a softer touch, drawing laughs from the audience while reminding the other Democrats of their need to be unified against President Trump. The biggest problem for Harris has been a cycle of where she does well in a debate - and her poll numbers go up. Then over the next month, those gains fade away. She does well in the next debate, and then her poll numbers go up. And they fade away again. Yes, she's the fourth strongest candidate when you look at the polls - but her debate performances have not translated into numbers which boost her into the Biden/Sanders/Warren tier.
5. Buttigieg still in the mushy middle of the race. While his name gets talked about a lot, while he's done fine in the debates so far, the polling for Mayor Pete Buttigieg continues to show that he's not in the top tier of Democrats with Biden, Warren, Sanders - and is struggling to stay in the middle with Harris, and not drop back towards the rest of the field. But one good note is that the Indiana mayor is still raising a lot of money, allowing him to set up a decent operation in Iowa, where he is doing much better in the polls than Harris. Some candidates may encounter money problems soon - it doesn't seem like Buttigieg is in that spot. On Thursday night, Buttigieg also gave the back of the hand to Julian Castro's attacks on Biden. "This is why presidential debates are becoming unwatchable," Buttigieg said.
6. Amy Klobuchar tries to get her campaign out of neutral. Klobuchar is one of a group of Democrats who certainly have the credentials to be in this race, but who have not been able to make the jump to light speed. "Houston, we have a problem," Klobuchar said early on Thursday night in talking about the need for Democrats to unite against President Trump. Klobuchar tried her best again in this debate to focus on how she got into politics, how she's a bit more moderate than Warren and Sanders, looking for a campaign spark. Klobuchar has not blossomed in Iowa as yet,as her more moderate brand of politics isn't really what many more progressive Democratic Party activists are looking for right now.
7. Booker looks for a primary breakout. In many ways, Cory Booker is in a similar situation as that of Klobuchar. Booker is a very popular guy with Democratic audiences on the campaign trail, and he has used his debate time to both spar and press his ideas. A positive vibe just seems to ooze from the guy naturally. But the polls continue to show Booker stuck along with so many other candidates, way down in single digits. Booker was asked one of the oddest questions in this debate - about the fact that he's a vegan. And he also weighed in on the hairstyle of the Canadian Prime Minister. A lot of voters like him, but Booker is nowhere near the top tier of candidates.
8. Beto tries for a campaign re-boot. In his home state, there were a lot of "Beto" signs around the debate site on Thursday, as the former Texas Congressman has been trying to inject new momentum into his campaign. Since the mass shooting in his home town of El Paso in early August, O'Rourke has put a heavy emphasis on gun control, as he staked out very clear ground on Thursday night that he would like ban - and even confiscate - military style assault weapons like the AR-15 and AK-47. "Hell yes, we're going to take your AR-15, your AK-47," O'Rourke said to cheers. Will gun control provide new hope for his campaign? The polls will tell us in coming weeks.
9. Castro raises eyebrows with Biden debate attacks. For a second straight debate, Julian Castro went after Joe Biden, and went after him hard, mocking Biden again for tying himself to President Obama on some issues but not on others. "He wants to take credit for Obama's work, but not have to answer any questions," Castro said, ripping Biden for not stopping large deportations of illegal immigrants under the Obama Administration. "Are you forgetting what you just said two minutes ago?" Castro said to Biden at one point on Thursday night. The Castro game plan didn't go over well with some; former Chicago Mayor Rahm Emmanuel said on ABC right after the debate that Castro came off as 'mean and vindictive.'
10. Andrew Yang might outlast most Democrats. Not only has Andrew Yang managed to raise enough money and get enough qualifying polls to stay in the debates, his combination of non-political and quirky positions has allowed him to get a good amount of attention - as he's doing better than about a dozen people in the 2020 race who do politics for a living. Yang doesn't mind poking fun at himself, he doesn't seem to care that Official Washington wants him to put on a tie for these debates, and doesn't worry about what people think of his plan for "Universal Basic Income," in which the government would give everyone $1,000 a month. I could see Yang sticking around for a while - whether or not he's really a threat to win his party's nomination.
11. All the others try to stay afloat. Let's face it, if you're one of those Democrats who failed to qualify for this debate - and if you can't qualify for the October debate - the end might be near for your campaign. Billionaire Tom Steyer has made the cut for October, and Tulsi Gabbard could as well. But the names of Williamson, Bullock, Ryan, Delaney, DeBlasio, and others are not likely to get in another big debate. And even if you are Booker, O'Rourke, Klobuchar, Yang, and Castro, it's an uphill fight to remain in the discussion for the 2020 Democratic nomination.
The Iowa Caucuses are February 3. The New Hampshire Primary is February 11. That is less than five months from now.
There are lot of miles still left to travel in the Democratic race. But the clock is ticking for a lot of the candidates.