There was almost a defensiveness when ABC News’s George Stephanopoulos informed the candidates participating in Thursday night’s third Democratic debate that they would spend some more time on health care. The subject is the one of most concern to voters, he explained, somewhat apologetically, so they were going to let all 10 candidates offer some thoughts.

In a vacuum, that makes sense. In practice, though? Each of the other debates in which the candidates have participated similarly included lengthy discussions of health-care policy at the outset. Yes, this was the first debate in which the three polling leaders — former vice president Joe Biden and Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.) — were onstage together. But the conversation wasn’t dramatically different from the ones that preceded it. A lot of “how will you pay for this” versus “it will reduce costs for families overall” that those who’ve watched have already seen — and which for those just tuning in was probably a level of detail deeper than would be revelatory.

The effect of focusing so intently on this one topic over and over is to leave less space for other also-important subjects. Shortly after Sen. Kamala D. Harris (D-Calif.) got offstage, her Twitter account noted the lack of discussion about reproductive rights. There was, however, another round of let’s-mention-our-Medicare-for-X-plans, to everyone’s delight.

By our count, there were 10 different topics discussed, grouped together fairly broadly. The flow of the evening’s almost three hours looked something like this.

The Sept. 12 debate

We’ve indicated an extended interruption at the tail end of the debate, when Biden was interrupted by immigration protesters.

There were only two ad breaks, which was nice in theory, though 90 minutes of discussing relatively nuanced policy details does tend to make one nostalgic for the mindless respite of advertising. (Though ABC’s inclusion of a spot promoting Sean Spicer’s “Dancing With the Stars” seemed an odd fit for the programming.)

Contrast that flow with the two-night debate at the end of the July.

The July 30—31 debate: Night 1

Night 2

You might have noticed that health care came up then, too.

Not every candidate got a chance to address every topic. The Washington Post has a tally of the overall time each candidate got to speak, but we broke that down roughly by subject, as well.

The most discussion by a candidate on one subject? Biden on health care, in part a function of his responding to comments from Sanders and Warren.

Sen. Amy Klobuchar (D-Minn.) and former congressman Beto O’Rourke of Texas weighed in on the fewest subjects, but each made a splash when given the chance.

O’Rourke spoke directly about removing AR-15 and AK-47 rifles from American homes, generating some attention on social media. It was a moment of strength, leveraging the tragedy that struck his hometown of El Paso shortly after the last Democratic debate.

Klobuchar, for her part, made a corny joke about the location of the debate — Houston; you can probably guess the joke if you try — earning some groans. But, hey, groans are attention, right?

This is where we say that the debate probably didn’t change anything, because that’s the safe thing to say and it has the happy tendency to be accurate. If, however, the debate had explored subjects that hadn’t been covered over and over, who knows? Maybe the foundation would have shaken a little more and the sorts of voters who watch these things — who, we’d guess, are more likely to have seen more than one debate than to just be tuning in for the first time — might learn a few additional policy positions.