Goodbye to all that. Now we know that Donald Trump would rip up the post-1945 world order, trash an “obsolete” NATO, lean toward a Japan with nukes rather than the “one-sided agreement” that leaves the United States responsible for Japanese defense, tell Saudi Arabia that it “wouldn’t be around for very long” without American protection, and generally make clear that “we cannot be the policeman of the world.”

So much for Pax Americana; it was a bad deal, you see, and in the Trump universe the deal is everything. American power and far-flung American garrisons may have underwritten global security and averted nuclear war for more than seven decades, but they cannot be sustained by the “poor country” the United States has become. Why? Because, he insists, the whole postwar setup is a scam.

That Trump could be the next president of the United States is no longer a fanciful notion. Americans don’t want business as usual; Trump is not business as usual. He’s ranting and schmoozing his way to the White House as the man who, through some alchemy, will make an anxious America proud again. The world — already more combustible than at any time in recent decades — may be about to become a much more dangerous place.

Trump, in interviews with my colleagues Maggie Haberman and David Sanger, said: “We have been disrespected, mocked and ripped off for many, many years by people that were smarter, shrewder, tougher. We were the big bully, but we were not smartly led.” America was “systematically ripped off by everybody. From China to Japan to South Korea to the Middle East, many states in the Middle East, for instance protecting Saudi Arabia and not being properly reimbursed for every penny that we spend.”