The most important news out of the fifth GOP debate was that Donald Trump vowed not to run as an independent. That pledge was a gift to Republicans; a third-party candidacy would almost surely elect Hillary Clinton.

Otherwise, the debate featured considerable bickering, which has become unappetizing. Positioning themselves as a circular firing squad is hardly the best path to the White House for the GOP hopefuls.

The much-anticipated blow-up of the Cruz-Trump bromance failed to materialize, but there were plenty of fireworks. CNN moderators goaded the nine participants to light into one another, quoting each other’s former slings and arrows, and were rewarded by numerous flare-ups between Donald Trump and Jeb Bush and also between Ted Cruz and Marco Rubio.

Occasionally, almost by accident, the questioners landed upon actual policy differences, most of which revolved around whether our immigration policies will keep us safe, the trade-off between privacy and security and how to confront ISIS.

The debate featured considerable bickering, which has become unappetizing. Positioning themselves as a circular firing squad is hardly the best path to the White House for the GOP hopefuls.

Once again, the host organization ended up much too big a part of the story, and in their quest for ratings trivialized what Americans have identified their number one concern: terrorism and national security.

In the sometimes detailed policy discussion, the outsiders on the stage appeared less than comfortable. Ben Carson, in attempting to answer a question about whether he was tough enough to lead our armed forces into battle, rambled on about how difficult it was to tell a child that he or she would have to undergo brain surgery. Responding to a question about how to confront North Korea’s Kim Jong-un, the retired neurosurgeon launched into a detailed listing of needed weapons upgrades. He will continue to fade.

Donald Trump flopped when asked how he would prioritize the nuclear triad, clearly ignorant of the issue. Marco Rubio stepped in to explain that the triad was our nuclear capability via missiles, airplanes and submarines.

Trump was also on the defensive over his earlier suggestion that we should close down the Internet to ISIS propaganda – an idea that Rand Paul dismissed as contrary to the First Amendment.

Similarly, Paul jumped on The Donald’s proposal to kill ISIS family members, saying it was a breach of the Geneva Convention. Strangely, (maybe we’re getting sucked into Trump’s alternate universe?) Mr. Trump was able to make those notions sound almost reasonable. As he says, ISIS jihadists might not care much for their own lives, but maybe they will care very much that their siblings or parents are killed in the fight. Similarly, when he suggests that the government should hire brilliant techies who can figure out how to block ISIS from publishing their vile propaganda on the Internet, you have to say – go for it!

Trump went after Jeb Bush on a couple of occasions, and was booed for his truculence. The moderator asked him to respond to Bush’s earlier declaration that Trump was “unhinged” when he suggested that no non-American Muslims be allowed entry into the country; Trump dismissed the criticism saying that   the former Florida governor was responding not to the idea but to the fact that he is so far down in the polls. Bush doubled down, describing Trump as the “chaos candidate,” who would surely become a “chaos president.”

Bush defended his ground adequately, remarking more than once -- to considerable applause -- that Trump would not be able to insult his way to the presidency, but he didn’t deliver a solid hit, and he needed one.

Carly Fiorina fell back on her experience as a CEO, and the importance of leadership. She brought nothing new to the debate, though her repeated suggestions that she could encourage technology companies to help in our intelligence gathering makes sense, as does her insistence that the government should be mining social media to uncover the bad guys.

The highlight of the two-hour slugfest was Senators Marco Rubio, Ted Cruz and Rand Paul duking it out over positions each had taken on immigration, defense spending and government snooping. After numerous “he said-she said” arguments, Chris Christie suggested that the bickering was a good example of why Americans are fed up with Washington. The audience seemed to agree.

That said, there are important differences in how these three would approach the job of defeating terrorism. Rand Paul continues to push a semi-isolationist approach, arguing against regime change and its attendant involvements, and distinguishes himself by declaring U.S. debt as our greatest threat. Given the heightened alarm over security, Paul’s concerns about excessive NSA surveillance, for instance, seem out of step. It is unlikely that Paul moved the needle, though he was more of a presence than in earlier confrontations.

It was the duel between Rubio and Cruz that was meatiest. Both men aspire to draft behind Trump; in case the front-runner begins to falter, each has a shot at taking the lead in early primaries. Cruz is increasingly expected to be the choice of conservatives and Rubio is the candidate most appealing to moderates, now that Bush appears unlikely to recover his early standing. They are facing off against each other with conviction, and it is a riveting contest – both smart, well informed and articulate.  

The “most improved” award goes to Chris Christie, who has enjoyed a surprising bounce in the polls. He forcefully brandished his experience as a prosecutor and governor, contrasting his actual handling of real problems the nitpicking arguments typical of lawmakers at work and, as it turns out, on the debate stage. When rival Paul taunted him over the Bridgegate scandal, Christie refused to take the bait. His maturity and self-control were impressive.

It was helpful that one of the participants reminded the audience that, despite obvious differences, any one of the candidates on the debate stage would be far more competent that Hillary Clinton or President Obama in keeping the country safe. The audience didn’t doubt it for a minute.

Liz Peek is a writer who contributes frequently to FoxNews.com. She is a financial columnist who also writes for The Fiscal Times. For more visit LizPeek.com. Follow her on Twitter@LizPeek.