Would a President Trump ruin America's foreign policy — or save it?

Donald Trump's blowout victory in Tuesday's Nevada caucuses — his third straight double-digit romp over his Republican presidential competitors — has thrown the GOP into an apparent crisis. Both Marco Rubio and Ted Cruz, supposedly the only viable competitors to Trump, are on the ropes, losing by more than 20 points to Trump. Trump has leads in most Super Tuesday contests. Who's going to stop him now?

It is time to take seriously the prospect of Trump's possible presidency — and the most compelling criticisms of it.

The most pressing issue is his power as president to wreck the rest of the world. It is a fact that Trump is more crudely oracular and unconvincingly sphinx-like on international relations than on any other issue. And where he is specific, it is hard to take him at his word. The net effect is that on foreign policy, he seems to be just winging it.

Well, you may say, America is resilient — deeply culturally sheltered from the destructive forces of democratization and globalization that have thrown so much of the globe into chaos. But the Mideast? The former Soviet space? East Asia? Africa? These places are fragile and dangerous in equal measure. They demand a degree of care and sophistication in policymaking that America does not.

Respected and trustworthy analysts are not sanguine about Trump's ability to supply what is needed worldwide. Peter Feaver, a Duke University professor of political science with experience in both the Clinton and (W.) Bush White Houses, recently made the following judgments: Trump's foreign policy promises will not come to fruition; he won't advance any new trade deals and much of what he does push will fail. What's more, his national security team will be "the least distinguished […] in modern memory. His administration will be hobbled by turnover, backstabbing, and other hallmarks of reality TV."

All bad — and plausible! — things. But then it gets worse. "Trump will isolate America from its allies and partners," adds Feaver (who supervised my undergraduate thesis). And, when he "gets in trouble, he will do something or say something that will embarrass the country." You probably don't need me to help you imagine how damaging these sorts of events could become.

But there is a sticking point in this case against Trump. The alternatives are not very appealing either. Given Hillary Clinton's track record on Russia, Libya, and Europe, it is very hard to put confidence in her ability to lead, avoid errors, correct for failures, and unite strong allies against daunting foes.

Marco Rubio, meanwhile, continues to distinguish himself as the most hysterical and hyperventilating candidate in the field on matters of national security and war. It is not just on domestic policy that he has clasped the Bush legacy in a suffocating bear hug. The point is not that neoconservatism stinks (it doesn't), but that Rubio's judgment on foreign affairs is as untested and immoderate as Trump's — if not moreso. Indeed, the one thing we know about Trump is he thinks Bush's foreign policy (in the first term, at least) was garbage, because it was produced in an echo chamber of abstract ideas foolishly delinked from reality. As dead-on as Feaver's warning seems to be, many Americans would be relieved to learn, however begrudgingly, that at least they could count on avoiding another Iraq, another Libya, or another Syria.

The national security establishment is tremendously powerful in the U.S. — sometimes for ill, but very often for tremendous good. It has many branches, filled with men and women of extreme dedication and great acumen. If Donald Trump is a complete idiot, he will rebuff these people and surround himself with the kinds of henchmen and amateurs who will guarantee that he goes down in history as failing beyond all measure to make America win again in the world.

Or perhaps Trump will take note of the foreign policy faceplant of well-intentioned novices like Jimmy Carter and staff the hell up on talent. Both the American people and the U.S. defense establishment are ready to turn the page on both Bush's and Obama's legacies abroad. In the most general and important sense, Trump offers that chance. He can screw it up royally, to be sure. (Presidents do!) But he can also have the sense, the savvy, and the pride to let our best civil servants throw their energies into a new grand strategy that actually works.

If you think Trump is now all but certain to ruin your country, the rest of the world is probably not high on your mind. But if you think America has been through far worse in the past, only for us to wind up far higher on top than so many of the planet's other peoples, you will likely agree that Trump's moment of truth will arrive — if it does — when the time comes to re-establish America's role in the world. At a moment when so little confidence has been placed in his rivals' ability to do just that, Trump likely faces a rare opportunity to make a global legacy Americans won't wear like an albatross.