E.J. Dionne: Booker broke through. Biden struck back. Harris got put in the hot seat.

Former Vice President Joe Biden listens as Sen. Kamala Harris, D-Calif., speaks during the second of two Democratic presidential primary debates hosted by CNN Wednesday, July 31, 2019, in the Fox Theatre in Detroit. (AP Photo/Paul Sancya)

Washington • Wednesday night’s debate was New Jersey Sen. Cory Booker’s breakthrough, former vice president Joe Biden’s comeback and California Sen. Kamala Harris’s turn in the hot seat.

If Tuesday’s Democratic debate was overwhelmingly ideological, Wednesday’s debate was intensely personal. The attacks flew across the stage, with Harris and Biden facing especially heavy fire. Sometimes, the volleys were rooted in philosophical differences — once again, health care was the subject of an often confusing set of exchanges around the costs, benefits and even the definition of Medicare-for-all — but they were just as often about the performance of the various contenders at challenging moments in their careers.

The confrontations came in waves. Harris, who surged in the polls by aggressively taking on Biden in June's debate, found herself at the other end of the sword. From the start, she was hit from all sides, particularly on her version of Medicare-for-all, which would allow participants to buy private insurance plans, as they can now under Medicare Advantage. She was criticized by Biden for the costs of her proposal and by other rivals for creating a system that would still allow private insurance companies to profit. Later, her record as California's attorney general was put on the griddle.

This allowed Booker to emerge. He had the disadvantage last month of not being on the same stage as Biden, allowing Harris her moment. This time, Booker offered a mixed portfolio. At times, he cast himself as the adult in the room, chastising everyone else for going after each other so fiercely. "The person that's enjoying this debate most right now is Donald Trump," Booker said during the free-for-all on health care. "That to me is dividing our party and demoralizing us in the face of the real enemy." He briefly tried to be the peacemaker again during a scrap over whether crossing the border should be decriminalized.

But he could not resist a gibe when Biden persistently declined to answer New York City Mayor Bill de Blasio's queries about whether as vice president he had tried to stop or reduce the deportation of undocumented immigrants during President Barack Obama's administration. Booker jumped at the opening: "You can't have it both ways," Booker snapped. "You invoke Barack Obama more than anybody in this campaign." It was a direct hit. Later, Booker assailed the crime bill Biden championed in the 1990s for creating the over-incarceration of African Americans that Biden now says he will roll back.

But Biden, who had been listless and at times confused under Harris' blows in June, gave as good as he got this time around. He hit back at Booker's police policies as mayor of Newark. He went after Harris hard on health care. He struck at former housing and urban development secretary Julián Castro's proposals to move illegal border crossings from criminal to civil courts.

He also tried to look crisp, knowing that looking old was a far greater enemy than anyone on the stage. Many of his answers were framed as 1, 2, 3 lists. It was far from a perfect performance. There were again moments when he looked tired and seemed happy when his time expired. But he hung in, to the relief of his supporters. If he suffered a serious drop in the polls after the first debate (from which he came back), he was unlikely to face another cliff this time.

For most of the debate's first hour, it seemed that Harris served as a kind of shield for Biden, with others on the stage seeking to displace her as one of the top four in the contest, along with Biden, Massachusetts Sen. Elizabeth Warren and Sen. Bernie Sanders of Vermont. Harris remained fluent, but she seemed surprised at times about how much grief she had to take across the board. It prevented an encore of her June triumph.

Perhaps because no one provided the ideological focal point that Warren and Sanders did the night before, the trailing candidates had more room to shine Wednesday. Colorado Sen. Michael Bennet also spoke powerfully, both as a critic of Harris's health plan and in a personal peroration on racial injustice. Castro was again very much in the mix, though he was not as significant a figure as he was in the earlier debate.

The upshot? Biden will remain on top, closing off room for other middle-of-the-road candidates to emerge. Booker now bids to join the golden circle along with Harris. And Warren and Sanders will remain at the center of the action, with Warren emerging from Round Two at her strongest point since the campaign began.

E.J. Dionne

E.J. Dionne is on Twitter: @EJDionne.