LONDON — What has Sarah Palin to do with the end of the world? I am not thinking of her former pastor, Ed Kalnins, who reportedly believes that the “End of Days” is nigh. Governor Palin takes a practical, rather than an apocalyptic view, of the future. It is enough to say that she has had five children, and that her son Track is about to serve in Iraq.

As it happens, the global press has been in an apocalyptic mood this week. Yesterday’s switching on of the Large Hadron Collider, the giant particle cruncher in Geneva, had been billed as the moment when the Earth might disappear into a man-made black hole. That would have been the ultimate act of hubris. It turned out to be the anti-climax of the century, but this did not prevent people enjoying the frisson of imminent doom.

So the end of the world isn’t nigh? Perhaps doomsday is merely postponed. Unfortunately, there really are people who are working hard to make it happen. I am thinking, first and foremost, of A.Q. Khan, the Pakistani scientist who confessed to passing nuclear secrets to North Korea, Iran, and Libya. The scientists working on the Iranian nuclear program, too, do so in the knowledge that they are serving a regime led by a fanatical president, Mahmoud Ahmadinejad, who prays for the end of the world every day, believing that this will mean the final triumph of Islam over the Christians, Jews, and other non-Muslims.

Then we have the ex-KGB men and their business associates who run the Kremlin. In Georgia, President Medvedev and Prime Minister Putin have demonstrated that they will cold-bloodedly cripple the best hope for democracy in the Caucasus, leaving a third of the country occupied and forcing hundreds of thousands to become victims of ethnic cleansing.

Mr. Putin already has wiped out at least 10%, some say as many as 25%, of the population during his bloody war in Chechnya. With gamblers like these in charge of the largest nuclear arsenal on the planet — America having largely dismantled its tactical nuclear forces — the future of humanity looks increasingly uncertain.

The Palin phenomenon is a reminder that America remains a true democracy, capable of throwing up leaders as improbable as they are able, unlike Europe, which has a tendency to revert to cosy oligarchy.

The European political class is much more homogeneous and also harder to penetrate. The career of Nicolas Sarkozy is a rare exception, but I fear that the French president’s image as a mould-breaker may have been oversold. His frenetic shuttle diplomacy between Paris and Moscow in recent weeks has yielded meagre results, and he continues to make the cardinal error of trusting the Kremlin’s promises. There is nobody else to seize the helm of Europe

Western civilization is still on trial.

Ever since that fateful day, seven years ago today, we have known that we were to be tested, in new and unforeseen ways, just as older generations were tested in the two world wars and the Cold War. This is a key moment in that process, for once again it falls to America to play the unique leadership role allotted to it by history, geography, and — let’s use an old-fashioned phrase — manifest destiny.

This would be a bad moment for America to lose its nerve. One of the strongest arguments for John McCain’s candidacy is that he did not lose his nerve over Iraq, at a time when the foreign policy establishment on both sides of the Atlantic came very close to doing just that. Not only has the surge been vindicated; so has the strategy that underpinned it, of relentless military pressure against the terrorists and the militias.

Now that President Bush is quietly applying the same strategy to Afghanistan, we may hope to see the same results there. It is vital that the re-emergence of Russian military aggression against its former imperial periphery, not to mention the potential threat posed by China to its neighbors, should not divert the West from the task of winning the War on Terror.

The former Soviet empire may be striking back, but we must not take our eye off the Islamist enemy. It won’t help us to deal with the Kremlin if we allow the restoration of the Caliphate.

It is against this background — the New Insecurity — that America’s presidential election takes place. Under such circumstances, the spectacular emergence of a tough American leader could have been predicted. Yet Mrs. Palin has taken the nation by storm and Washington D.C. by surprise. She has given the McCain campaign a badly-needed shot in the arm, but the electors still need to have it explained to them why it might be wise at this particular historical juncture to prefer a grizzled Vietnam vet to a slick Harvard lawyer.

Though Americans know the world is a dangerous place, it can seem too far away to matter as much as more immediate concerns. I am confident, however, that over the remaining weeks of the campaign, Mrs. Palin’s gifts as a communicator will persuade voters that they will sleep more easily in their beds with Mr. McCain in the White House. She must convince them that Mr. McCain is, if not another Reagan, then at least Reaganesque.

That is how Mrs. Palin could help to prevent the end of the world. Her whole life has been a preparation for this moment. Her emergence at this juncture is not merely America’s good fortune — it could be providential for the planet.

Mr. Johnson is the Editor of Standpoint.