One of the biggest challenges of preparing for a nationally televised political debate is the uncertainty. You cannot know what questions you will be asked, so you must prepare for dozens of possible questions on a range of topics and keep it all together in your head and ready to access at a moment's notice.

The Democratic candidates did not have this problem when they walked onto the stage for the CBS presidential debate on Saturday. Shortly after terrorists launched a series of devastating attacks in Paris on Friday night, CBS announced that the entire debate — later whittled down to the first 30 minutes — would focus on the attacks and related policy issues.

Yet somehow, even though the candidates knew the subject ahead of time and could easily have anticipated many of the individual questions, all three of them undeniably flunked it. Even with 24 hours to prepare and full staffs to help them do it, at no point did anyone offer anything resembling an answer to the question that this was all about: What would they do about ISIS?

If you were an American — or a European or a Syrian or an Iraqi, for that matter — tuning in to learn how the next Democratic presidential nominee thinks about the challenge of ISIS, then you might well come away from this debate thinking the candidates aren't prepared even to stumble their way through a question about ISIS, much less take on the group itself. Maybe that conclusion would be wrong — maybe in fact some or even all of the candidates would be brilliant against ISIS — but you'd have little way of knowing it from this debate.

The worst answer of the night came from Hillary Clinton

No one shined in this part of the debate, and everyone failed. But possibly the worst answer of the night, from Hillary Clinton, came in response to the most easily anticipatable question: Americans are not thrilled with the Obama administration's effort against ISIS, and yet you were a senior member of the Obama administration, so why should Americans trust you to take on ISIS?

The video here shows Clinton's answer, and it really has to be watched to understand just how poorly it went.

She rambled incoherently, at some points simply listing things — irrelevant lists of buzzwords were a major theme of the evening — and offered neither policy ideas nor even vague rhetorical themes. She half-attempted to put the onus of responsibility on George W. Bush over his administration's understanding with Iraq on not leaving American troops there, but the way she described it was so confusing and dissembling that I doubt most people even knew what she was talking about.

The closest she came to putting together a coherent sentence was when she said "it cannot be an American fight" as part of a quote that I guarantee you will appear on Republican attack ads if she wins the nomination. I believe she was attempting to say either that United States troops cannot play the role of ground army against ISIS or that the larger effort against ISIS must involve local allies and cannot be led by the US alone. It's not clear, and we debated this some in the office. But the point is that Clinton conceded some political ground for basically nothing — she neither scored political points nor articulated a foreign policy position. It was all downside.

The rest of Clinton's answers had the political merit, at least, of being far too nonsensical to do her much damage. Consider, for example, a few more of her quotes.

On whether her support for the US-backed intervention in Libya was a mistake:

The Libyans turned out for one of the most successful fairest elections that any Arab country has had. They elected moderate leaders. Now there has been a lot of turmoil and trouble as they have tried to deal with these radical elements which you find in this arc of instability from north Africa to Afghanistan. And it is imperative that we do more not only to help our friends and partners protect themselves and protect our own homeland, but also to work to try to deal with this arc of instability, which does have a lot of impact on what happens in a country like Libya.

On whether her vote in support of the 2003 Iraq invasion was a mistake:

Well, I think it's important we put this in historic context. The United States has, unfortunately, been victimized by terrorism going back decades. In the 1980s, it was in Beirut, Lebanon, under president Reagan's administration, and 258 Americans, Marines, embassy personnel, and others were murdered. We also had attacks on two of our embassies in Tanzania and Kenya. When my husband was president. Again, Americans murdered. And then, of course, 9/11 happened, which happened before there was an invasion of Iraq. I have said the invasion of Iraq was a mistake. But I think if we're ever going to really tackle the problems posed by jihadi extreme terrorism, we need to understand it and realize that it has antecedents to what happened in Iraq and we have to continue to be vigilant about it.

Even her opening statement — which she had the opportunity to memorize in advance — was gibberish:

Well, our prayers are with the people of France tonight, but that is not enough. We need to have a resolve that will bring the world together to root out the kind of radical jihadist ideology that motivates organizations like ISIS, a barbaric, ruthless, violent jihadist terrorist group. This election is not only about electing a president. It's also about choosing our next commander in chief. And I will be laying out in detail what I think we need to do with our friends and allies in Europe and elsewhere to do a better job of coordinating efforts against the scourge of terrorism. Our country deserves no less because all of the other issues we want to deal with depend upon us being secure and strong.

When you look at the individual words, they make sense in a foreign policy presidential debate. But they have been strung together in a way that makes little sense, and often has nothing to do with the topic at hand. At best, you have meaningless platitudes like, "We have to do more on foreign matters." But mostly it's just gobbledegook.

Martin O'Malley made every mistake Clinton made but a little bit worse

If former Maryland Gov. Martin O'Malley is indeed angling to be Hillary Clinton's vice presidential pick, as some speculate, then he played to form on Saturday night by following Clinton's stumbling lead, every painful step of the way, but still underperforming her just a little bit.

Take, for example, his statement on what to do about ISIS. Again, I need to reiterate, this is the question that every candidate knew absolutely and hours in advance would be asked. Yet, like Clinton, what he came in with was a bunch of rambling that veered between nonsense and pablum:

This actually is America's fight. It cannot solely be America's fight. America is best when we work in collaboration with our allies. America is best when we are actually standing up to evil in this world. And ISIS, make no mistake about it, is an evil in this world. ISIS has brought down a Russian airliner. ISIS has now attacked a western democracy in France. And we do have a role in this. Not solely ours, but we must work collaboratively with other nations. The great failing of these last 10 or 15 years, John, has been our failing of human intelligence on the ground. Our role in the world is not to roam the globe looking for new dictators to topple. Our role in the world is to make ourselves a beacon of hope. Make ourselves stronger at home, but also our role in the world, yes, is also to confront evil when it rises.

"Make ourselves stronger at home, but also our role in the world, yes, is also to confront evil when it rises." Too long to put on a bumper sticker, but maybe it'll fit on an inspirational poster.

O'Malley also got an entirely foreseeable question on whether he was prepared to handle tough foreign policy challenges as someone with little international experience. In his answer, he seemed to start each sentence with a prepackaged talking point — fair enough, it's worth planning ahead — but then immediately lose the threat, forget the point he wanted to make, and then try again with a totally different talking point:

John, the world is a very dangerous place but the world is not too dangerous a place for the United States of America provided we act according to our principles, providing we act intelligently. Let's talk about this arc of instability that secretary Clinton talked about. Libya is now a mess. Syria is a mess. Iraq is a mess. Afghanistan is a mess. As Americans, we have shown ourselves to have the greatest military on the face of the planet, but we are not so very good at anticipating threats and appreciating just how difficult it is to build up stable democracies, to make the investments and sustainable development that we must as a nation if we are to attack the root causes of these sorts of instability. And I wanted to add one other thing, John, and I think it's important for all of us on this stage. I was in Burlington, Iowa, and a mom of a service member of ours who served two duties in Iraq said, "Governor O'Malley, please, when you're with your other candidates and colleagues on stage, please don't use the term 'boots on the ground'. Let's don't use the term 'boots on the ground'. My son is not a pair of boots on the ground. These are American soldiers and we fail them when we fail to take into account what happens the day after a dictator falls and when we fail to act when a whole of government approach with sustainable development, diplomacy, and our economic power in align with our principles.

I am literally baffled by these answers from Clinton and O'Malley.

I can understand being ruffled by a tough question or caught off guard by a shot from another candidate. What I cannot understand is this: All the candidates knew 24-plus hours in advance that they would get some form of the question, "What would you do as president about ISIS?" They knew they would have just a few seconds of airtime to answer.

All they had to do was formulate some talking points — in many cases already available on their own websites! — memorize them, and spit them back out when the time came. Couldn't be easier. Neither seems to have done this.

Bernie Sanders came into the debate not wanting to talk foreign policy and was surprisingly successful at that

In the hours before the CBS debate, Sanders's campaign team fought with CBS not to make foreign policy and national security the entire focus of the debate. And they succeeded, getting the network to dedicate only the first half-hour to those topics.

When the debate began, the first prompt was for each candidate to give a one-minute opening statement specifically on the attack in Paris. Sanders's response to this was pretty simple: He dedicated two sentences to the attack and spent the rest of it talking about American economic inequality. He made no transition and no attempt to link the two.

Economic inequality is indeed an important issue. But by dodging the prompt of talking about Paris, Sanders ended up sending the same message that his campaign team sent when it lobbied CBS not to focus on the attacks: He is just not really prepared to talk about foreign policy and national security. Being unable to discuss those issues does not lend a lot of confidence he would be well-suited to lead on them.

The irony is that Sanders actually had the best performance of the three candidates on foreign policy. It's not that he offered brilliant ideas for dealing with ISIS, or even any ideas at all. Like the other candidates, he said nothing of value about what he would do. Unlike the other candidates, he at least did a good job of articulating what he would not do.

Sanders made clear argument for why he would not maintain heavy military spending on non-terror threats and why he would not support regime change. Fair enough! Viewers hoping for answers on the topic of the night, what to do about ISIS, did not get an answer.

The closest viewers got was this, in response to a question from the moderator on whether it was important to use the phrase "radical Islam" when talking about terror groups:

I don't think the term is what's important. What is important to understand is we have organizations, whether it is ISIS or al-Qaeda, who do believe we should go back several thousand years. We should make women third-class citizens, that we should allow children to be sexually assaulted, that they are a danger to modern society, and that this world, with American leadership, can and must come together to destroy them. We can do that. And it requires an entire world to come together, including in a very active way the Muslim nations.

Sanders separately argued that the ISIS conflict was "a war for the soul of Islam" and that it was to "the Muslim nations in the region" to "lead the effort" with "support" from the US.

Also unlike the other candidates, Sanders was pretty good at deflecting the questions he did not want to answer. When the moderator tried to nail him down on how many Syrian refugees he thinks the US should accept, a subject on which he's been vague, Sanders said he couldn't give a number, and then pivoted to arguing that US military spending was too high.

He scraped through it, in other words, without the self-inflicted of the other candidates — but that's about it. So I suppose on that metric, he won, but it's not much a victory.