If there’s any lesson from Tuesday’s debate, it’s that six months after his entry into the Republican presidential race, no one has any better idea of how to handle Donald Trump than when he first got in.

Las Vegas highlighted how Trump has established alpha-dog dominance in the Republican field. He’s not only the front-runner according to national polls, he’s a front-runner other candidates are literally afraid to criticize in his presence.

Everyone’s happy to have his blessing. When Trump pronounced Ted Cruz “just fine” at the end of the debate, the Texas senator appeared as tickled as if he’d just won the Presidential Medal of Freedom or an Academy Award.

Ben Carson seemed perfectly pleased to accept Trump’s compliment as “one of the finest men” — even though Trump had been denouncing him as pathological and a liar a couple of weeks earlier. Even Jeb Bush eagerly exchanged a low-five with the mogul during one of the early debates.

It’s Bush, of course, who has taken it upon himself to constantly go after Trump in the debates, and it always ends in roughly the same way. Bush criticizes Trump and calls him unserious. Trump makes faces, then interrupts Bush to mock him in harshly personal terms and cite his low poll numbers. Bush calls Trump unserious some more. Trump interrupts and makes more faces.

Las Vegas was no different, even if Bush was more adept at grappling with Trump than he had been in past exchanges. It’s possible to imagine party elders finding Bush’s anti-Trump tack satisfying and brave, but it has gotten nowhere. If scolding Trump for being unserious, irresponsible, divisive and hurtful were the keys to bringing him down, Bush would have devastated Trump by now.

Bush is an accomplished public servant and profoundly decent man whose theory of the race has been that the party needs an adult. But the party wants a leader. While there’s overlap between those two things, they aren’t identical. An adult makes sure everyone is operating within the bounds of established rules; a leader changes the rules.

The three most vibrant non-Trump contenders are the three who have been most careful to sidestep the mogul: Ted Cruz, Marco Rubio and Chris Christie. This may be a coincidence, or it may have something to do with their ability to rationally calculate their political interest.

It’s Cruz who has sidestepped Trump most determinedly. Rubio and Christie have slapped back when hit by Trump. Cruz appears to live in mortal fear that Trump might look at him crosswise. The several days prior to the Las Vegas debate, Cruz’s campaign appeared to have entered its “Thank you, sir, may I have another” phase. Trump questioned Cruz’s religion and his judgment, and Cruz brushed it off as a trifling misunderstanding between stalwart foes of the establishment.

Cruz’s submissiveness to Trump is — depending on your tolerance for insincerity in the service of a larger political goal — either appallingly or gloriously disingenuous. It couldn’t be more transparent if Cruz had been caught on tape at a private fundraiser acknowledging that it was part of his plan to defeat Trump — and, in fact, he was! Still, by honoring Trump’s implicit rule that if you demonstrate respect for him, he’ll probably leave you alone, Cruz has so far avoided a Trump onslaught.

Republican insiders find the Cruz maneuver galling. But consider this feat: Cruz has managed to maintain a fragile truce with Trump while surging past him in the crucial first state. If Trump is overly bothered by Cruz leading him by 10 points in Iowa, according to the widely respected Des Moines Register poll, and potentially dealing him a damaging blow at the outset of actual voting, he hasn’t given much sign of it yet.

Those who think Ted Cruz is obliged to be more openly anti-Trump should consider that so far it is the shrewd Texan who has made the most progress in stopping him.

Rich Lowry can be reached via e-mail: comments.lowry@nationalreview.com.