Let’s start with the most mind-boggling and entirely self-created problem. The Democratic National Committee, in an act of political malpractice, decided to extend the period to qualify for the October debate, which means some candidates who didn’t make the September stage (such as Steyer) could qualify for October’s debate. That not only defeats the purpose of narrowing the field in a timely manner, but actively encourages candidates to stick around. (Hey, just one more month!) The grown-ups in the party should demand that the criteria for debates in November, December and beyond become increasingly difficult to meet so we are down to a reasonable number (six to eight?) by the end of the year. Right now, all the DNC is doing is giving marginal candidates incentive to beat up on the viable ones.

Given the refusal to limit subject matter to one topic or even a range of topics, the debate nevertheless can be redesigned to become more informative and coherent. ABC News should start by asking fewer questions and thereby allowing more debate on a topic. Go wild, and give them 30 minutes to discuss how they’d reestablish U.S. leadership in the world.

Instead of baiting the candidates to attack one another (“What’s wrong with your opponent’s plan”), the candidates really need to explain their own ideas. Candidates should be queried about what’s in their proposals before picking fights with other candidates who also haven’t explained their plans. Moderators can ask some follow-ups to tease out specifics before inviting criticism.

Take student debt. What is the problem Ms. Candidate is trying to solve? Why is that problem — instead of say, raising college completion rates or providing college alternatives — important to solve? Who is helped and who is taxed to pay for this?

As for the candidates, they’ve been informed by experience: Directly attacking an opponent is not a recipe for success. Instead, they might want to focus on how President Trump has blown it on a given topic, how his missteps, negligence or cruelty has hurt people, what the Democratic contender will say or do to expose the president’s failure, and why everyone concerned about that issue would be better if Trump were gone.

This may seem elementary, but the first two debates haven’t worked like this. There have been a slew of scattershot questions mostly designed to pit candidates against one another, indecipherable fights about details they still have not explained and wasted time that could have been used to remind viewers of Trump’s failings.

Finally, there have been a bunch of topics that have been virtually ignored in earlier debates that need discussion:

Does the debt matter, and what would you do about it?

How would you reset relations with China, Russia, Saudi Arabia, etc.?

What is the nature of the terrorist threat today (foreign and domestic), and how would you protect Americans?

What do we do about the growing urban/rural divide?

How do you plan on improving race relations?

How do you assist workers displaced by automation or trade?

What’s your plan on child care?

This might be a lot to ask, but Democrats have a lot riding on making the case against Trump in front of huge audiences. They should figure out how to accomplish that basic task.