A strong night for Joe Biden and Cory Booker

The two winners in Thursday’s Democratic debate: Joe Biden and Cory Booker.

For those Democratic presidential hopefuls who have premised their hopes on Biden’s collapse, the former vice president delivered a clear message: Don’t bet your campaign on it.

Biden is never a particularly polished debater, but on the stage at Texas Southern University, he stayed as the center of things throughout, defended his record ably, and established himself as the leading member of the mend-don’t-end Obamacare camp.

Health care was also where Castro made a big blunder. It came as the former secretary of Housing and Urban Development strove to draw his own health-care-plan distinction with Biden over a plan-enrollment detail. All well and good, but Castro then played the age card, and in a completely unsubtle and off-putting fashion.

“Are you forgetting already what you said just two minutes ago?” Castro asked, and not just once, but several times, in an obvious attempt to portray Biden as forgetful and uncertain. That is, doddering.

Two points: (1) Biden wasn’t. (2) Ugh.

One much-anticipated story line was how Biden would fare on the stage with Elizabeth Warren, given her reputation as the candidate of substance and plans. The view here is that he more than held his own.

That was particularly true on health care, as the first segment of the debate quickly honed in on the split between advocates of a no-private-insurance single-payer system — basically Bernie Sanders and Warren — and those who support adding a Medicare-like public option to the Affordable Care Act, but oppose taking private insurance away from those who want to keep it.

After spending the first dozen debates — what, you say there have been only two others? — largely on the defensive, Biden went on offense, pressing Warren and Sanders about the cost and financing of their single-payer system. He got little by way of answers.

But it was fellow Obamacare supporter (and South Bend, Ind., mayor) Pete Buttigieg — who cleverly describes his plan to add a public option to the Affordable Care Act as “Medicare for all who want it” — who made perhaps the most telling political point about the Sanders/Warren approach: It doesn’t trust the American people to make their own decisions regarding what health care coverage works best for them.

(Memo to future debate moderators: Dig in on this issue and develop better, smarter questions. Queries that largely leave it up to one candidate to critique another on health care complexities have about run their productive course.)

Of the top three, this was not a good night for Sanders, who was grim, intense, and hoarse, but still speaking in a near-shout for much of the evening. It’s hard to imagine anyone looking at that performance and saying: Yes, I could really see him as president.

Warren used her biography effectively, but she got lost for considerable portions of the debate.

Booker’s strong night was less a matter of one or two moments and more his overall performance. The New Jersey senator spoke knowledgeably, passionately, and impressively on a range of domestic subjects, from racism to gun violence to poverty to education. He even had the courage to say a kind word about charter schools; as recently as Barack Obama’s presidency, charters enjoyed considerable Democratic support, but they have since become the target of all-out opposition — and wild-eyed allegations — from the teachers’ unions, a core Democratic constituency and funding source.

Starting with an opening statement addressed directly to Donald Trump, Senator Kamala Harris of California seemed to be reaching too hard for a TV-highlights hit. Her best, and most heartfelt, moment came when she noted how much having black teachers increased the likelihood that a black student will go on to college.

Andrew Yang, who has developed a campaign cool all of his own, was loose and funny and self-deprecating about his early failures as an entrepreneur, Beto O’Rourke passionate and forceful about gun violence and assault weapons. Minnesota Senator Amy Klobuchar declared her more moderate approach rhetorically, but didn’t really demonstrate it substantively.

So, big — well, medium-size — takeaways? Look for this debate to hearten Biden supporters and sharpen the sense that Warren has overtaken Sanders in the left lane. And to give Booker some important new oxygen.

Scot Lehigh can be reached at lehigh@globe.com. Follow him on Twitter @GlobeScotLehigh.