Here are the 5 key takeaways from the ABC News Democratic debate

Amid blows over pivotal issues, some unity.

As Democrats descended into Republican territory for Thursday’s debate in Houston, Texas, they made their pitches to voters with the hope of creating a battleground opportunity in 2020. Over the course of nearly three hours, the ten candidates exchanged blows over pivotal issues including health care, gun legislation, climate change, education and criminal justice.

The debate also featured a rare moment of unity on the heels of tragedy that took place in the border town of El Paso, Texas. Despite their differences regarding the best way to pursue gun policy reform, all of the candidates rallied around former Congressman Beto O’Rourke, an El Paso native.

The center stage tangle over health care

The first-time faceoff between Biden and Warren almost immediately devolved into a pile-on over health care across all wings of the debate stage. With Warren on his left, and Sen. Bernie Sanders to his right, Biden, the current top-polling front runner, was pelted with attacks on all sides.

While Warren and Sanders questioned whether Biden’s plan, which would build upon Obamacare rather than completely overhaul it, went far enough, Biden staunchly defended the former president’s landmark health care bill.

“I know that the senator says she’s for Bernie. Well I’m for Barack. I think Obamacare worked,” Biden said. “This is about candor, honesty, big ideas.”

Biden also questioned how the two progressives flanking him on stage would pay for their plans.

“My distinguished friend, the senator on my left, has not indicated how she pays for it,” Biden said in reference to Warren’s defense of a “Medicare For All” plan.

“And the senator has, in fact, come forward and said how he's going to pay for it, but it gets him halfway there,” Biden added in a pivot to Sanders.

Biden also argued Warren’s plan would result in tax hikes for the middle class, which the Massachusetts senator didn’t overtly deny. Instead, Warren took a swipe back by insisting she “actually never met anybody who likes their health insurance company.”

The debate over “Medicare For All” exposed deep divides between the progressive and more moderate candidates on stage, including current Senate colleagues.

Sanders was put on the spot for his backing of “Medicare for All” by Sen. Amy Klobuchar. While Sanders claimed ownership over writing the plan, which he said would would be the most cost-effective policy for providing Americans with health care, Klobuchar insisted otherwise.

“While Bernie wrote the bill, I read the bill,” Klobuchar jabbed.

Former colleagues face off

While the former vice president invoked the accomplishments of President Obama on health care, he also fielded a sharp attack from one of his former administration colleagues. In a testy exchange, former Housing and Urban Development Secretary Julian Castro seemed to question Biden’s mental fitness as he argued over the difference between automatic enrollment and opting-in for coverage.

“That's a big difference, because Barack Obama's vision was not to leave 10 million people uncovered. He wanted every single person in this country covered. My plan would do that. Your plan would not,” Castro said.

As Biden said Americans would not have to buy into coverage under his plan, Castro followed up with a claim that the former vice president contradicted himself.

“You just said two minutes ago that they would have to buy in,” Castro shot back. “Are you forgetting what you said two minutes ago? Are you forgetting already what you said just two minutes ago?”

In fact, two minutes earlier Biden stated people would be enrolled in Medicare if they could not afford health insurance.

“Anyone who can't afford it gets automatically enrolled in the Medicare-type option,” Biden said, later adding, “If you want Medicare, if you lose the job from your insurance company, from your employer, you automatically can buy into this.”

Harris pivots from challenging Biden to taking on Trump

After briefly rising and falling in the polls following a headline-grabbing debate performance in June, Sen. Kamala Harris on Thursday pivoted away from the theatrics that marked her early performances and focused on targeting a rival not on the debate stage: President Trump.

“I have a few words for Donald Trump,” Harris said, turning to speak directly to the camera. “What you don't get you is that the American people are so much better than this.”

The California senator added that her campaign is focused “on our common issues, common hopes and desires” and that she will work to unify the country and turn “the page for America.”

“And now, President Trump, you can go back to watching Fox News,” Harris said after calling out the president.

And later in the debate, amid a fiery discussion on Medicare for All, Harris again used her time to address the president. “At least five people have talked, some repeatedly on this subject, and not once have we talked about Donald Trump,” Harris said. “So let's talk about the fact that Donald Trump came into office and spent almost the entire first year of his term trying to get rid of the Affordable Care Act.”

Harris’ campaign has somewhat stumbled after initially seeing a bump in polling following a blockbuster moment in the first debate when the California senator criticized Biden for his history of working with segregationists and opposing school busing.

Candidates defend records on race, praise O’Rourke’s response to El Paso shooting

The issue of race in America took center stage during Thursday night’s debate -- and while most of the candidates called out Trump for widening the racial divide, a number of the Democrats on stage were asked to defend their own record.

ABC News Correspondent Linsey Davis asked Mayor Pete Buttigieg, “You've been struggling with issues around race in your own community. You've also said that anyone who votes to re-elect President Trump is, at best, looking the other way on racism. Does that sort of talk alienate voters and potentially deepen divisions in our country?”

The South Bend mayor looked to divert his response away from his record and toward Trump, saying, “I believe what's deepened divisions in the country is the conduct of this president, and we have a chance to change all of that.”

And when confronted about her record in law enforcement by Davis, Sen. Harris seemed ready to respond: “I'm glad you asked me this question, and there have been many distortions of my record.”

Harris went on to defend her service, promising to close private prisons and to hold law enforcement, including prosecutors, accountable. The former California attorney general added that her experience would allow her to fix the system “from the inside.”

“I will have the ability to be an effective leader and get this job complete,” Harris said.

Another major moment: Amid the heated discussion on racial issues and gun control, candidates found a brief moment of unity Thursday night, offering support for O’Rourke in his home state for his response to the recent mass shooting in El Paso which targeted Latinos.

“I want to commend Beto for how well he has spoken to the passion and the frustration and the sadness after what happened in his hometown of El Paso. He's done a great job with that,” Castro told his fellow candidate.

The former vice president also commended O’Rourke for how he handled the shooting, first calling the former congressman “Beto” before apologizing. “Excuse me for saying Beto," Biden said, to which O’Rourke replied, "That’s all right, Beto's good.”

“The way he handled what happened in his hometown is meaningful. The look in the eyes of those people, to see those kids, to understand those parents, you understand the heartache,” Biden said.

And in one of the more passionate moments from Thursday’s debate, O’Rourke argued for stricter gun control by telling an emotional story of visiting with victims of the shooting.

“I met the mother of a 15-year-old girl who was shot by an AR-15 and that mother watched her bleed to death over the course of an hour because so many other people were shot by that AR-15 in Odessa, in Midland. There weren't enough ambulances to get to them in time,” O’Rourke said. “So, hell yes, we're going to take your AR-15, your AK-47. We're not going to allow it to be used against fellow Americans anymore.”

Buttigieg shares his personal story of coming out

All ten candidates were asked to close the debate by sharing some of their professional setbacks in order to demonstrate their ability to be resilient leaders if elected president.

The question drew a wide array of responses, including Buttigieg’s personal story of coming out under the “Don’t Ask, Don’t Tell” policy, before becoming an elected official in a conservative state.

“When it came to professional setbacks, I’d wonder whether just acknowledging who I was, was going to be the ultimate career-ending professional setback,” Buttigieg said. “I came back from the deployment and realized that you only get to live one life, and I was not interested in not knowing what it was like to be in love any longer, so I just came out.”

“I had no idea what kind of professional setback it would be, especially because inconveniently, it was an election year in my socially conservative community,” he continued. “What happened was that when I trusted voters to judge me based on the job that I did for them, they decided to trust me and re-elected me with 80% of the vote. And what I learned was that trust can be reciprocated, and that part of how you can win and deserve to win is to know what's worth more to you than winning.”

As the first openly gay person to run for U.S. president, Buttigieg’s account offered a reminder of the historic nature of the diversity among this field of candidates.

ABC News' MaryAlice Parks, Kendall Karson and John Verhovek contributed to this report.