There are two things it is futile to try and predict a year or more ahead: the exchange rate of the dollar and the next president of the United States. But let's just suppose that the most probable thing - based on current opinion polls - actually happens. By that I mean that Hillary Clinton wins the Democratic party's nomination and Rudy Giuliani wins the Republican party's.
If that is the choice Americans confront on polling day (which admittedly is still 14 months away), then Rudy Giuliani could very well emerge as the next president of the United States. Even if Barack Obama agrees to be Senator Clinton's running mate on a politically correct dream ticket. Even if Michael Bloomberg, Giuliani's Croesus-like successor as Mayor of New York, runs as an independent third candidate.
Let me be clear: I do not think Giuliani is the best of the Republican candidates. I have been playing a (frankly minor) role as an adviser to John McCain, who never ceases to impress me with his guts, grit and gumption. His campaign has been beset by difficulties, not the least of which has been McCain's unflinching consistency on the hot topics of Iraq and immigration. But it's still too early to write him off.
Nevertheless, the fact is that Giuliani is, and has been for some time, the clear front-runner. Nor does it seem very likely to me that he will be overhauled by Fred Thompson, the Reagan wannabe who so manifestly lacks the Gipper's passion and vision. This week Giuliani is taking time out from pressing the unyielding flesh of Iowan farmers to visit London, where he will give the first Margaret Thatcher Lecture at the Atlantic Bridge think tank. It is time to start pondering what a Giuliani presidency might mean for America - and for the rest of us.
Conventional wisdom among political commentators is that Rudy is about as welcome in Middle America as a subprime mortgage is on Wall Street these days. It's not just the liberal positions he took on abortion, gun control and gay rights when he was Mayor of New York. It's also his distinctly messy private life. To paraphrase Oscar Wilde, to be divorced once is unfortunate; twice looks like carelessness. Worse, Rudy is suspected by some Bible Belters of doing more than merely paraphrasing Oscar. He has been captured on camera cavorting in drag. While he was between wives, he moved in with a gay couple. Asked recently about his religion, he gave a true New Yorker's answer: "I pray like a lawyer. I try to make a deal: 'Get me out of this jam, and I'll start going back to church.' "
No wonder Mitt Romney's Mormon faith suddenly seems less of a handicap. Although technically entitled to practise polygamy, Romney is (as he likes to repeat) the only Republican contender who has had only one wife. Giuliani's two children are so sick of their father's antics they are unlikely to vote for him. By contrast, Romney's progeny resemble the Osmonds: handsome, wholesome and 100 per cent devoted to Dad.
Yet the polls are telling us something. In an insightful portrait in last week's New York Times Magazine, Matt Bai argued that it's precisely Rudy Giuliani's edgy persona that is his biggest asset. Six years after al-Qaeda's attacks on New York and Washington, with American soldiers fighting and dying in two distant and dangerous lands, Americans may well be in the market for a proven hard-ass who gets results, regardless of what he gets up to at night. Giuliani will always be remembered for hitting the right note of unbowed defiance after the destruction of the World Trade Centre. But his real claim to fame is that he was the guy who turned around the self-styled capital of the world.
I remember visiting the pre-Giuliani Manhattan. It was like a one long episode of Kojak. The professions then open to young New Yorkers were dealer, hood, hooker, junkie, pimp - or bent cop. Yet by the time I moved to the city, not long after 9/11, the analysts outnumbered the psychos. Kojak had been replaced by Seinfeld. A large share of the credit for that transformation belongs to Giuliani. His presidential bid is based on the notion that what worked for the world's capital can work for the world itself.
America, Giuliani says, must remain "on offense" to win the "terrorists' war on us". What, like George Bush? No, no, no, no, no. In common with nearly all the Republican candidates, Giuliani's hero of choice is Ronald Reagan. But he also makes a point of likening himself to Winston Churchill. No doubt this week he'll follow Gordon Brown's example and add Lady Thatcher to the list of role-models (just don't start dressing like her, Rudy).
The Churchill parallel is the one that worries me. It shows that Giuliani buys the idea that since 9/11 America has been fighting World War III (or IV, if you like to give the Cold War a number). Time and again in the last six years, leading Republicans have drawn these naive historical analogies. Al-Qaeda are Islamofascists. 9/11 was Pearl Harbor. Saddam Hussein was Hitler. The fall of Baghdad would be like the liberation of Paris. And so on. Now it's Rudy's turn. "We should try to accomplish [in Iraq] what we accomplished in Japan or in Germany," he says. What, like bombing the place flat?
The reality is that the threat posed by Islamist terrorism today is wholly different from the threat posed by the Axis powers in 1941-2. To judge by Osama bin Laden's latest rant, he aims at mass conversion, not conquest (with low-interest loans as the latest inducement). The Islamists have thousands rather than millions of trained warriors. Their most dangerous weapons are landmines and rocket-propelled grenades, not aircraft carriers and armoured divisions. The total number of American fatalities that can be attributed to this supposed world war is just over 6,000 (adding together 9/11 victims with US passports and the service personnel killed in action in Iraq and Afghanistan). On average, the Axis powers killed around 20,000 Allied soldiers and civilians a day.
The trouble is that the more Americans imagine they are in a world war, the less attention they pay to the more profound strategic threats their country currently faces. I can think of four in particular: the descent of the Greater Middle East into a large-scale war, the disintegration of the system of nuclear non-proliferation, the escalating competition between developed and emerging economies over scarce raw materials and the breakdown of the system of multilateral trade liberalisation.
Taken together, these challenges will sorely test whoever occupies the White House after George W Bush. Has Giuliani given any of them serious thought? Does he have any strategic vision beyond preventing another 9/11 (his nightmare, he says, is an Iranian-made dirty bomb "in London or Rome or America")?
In his interview with Bai, Giuliani kept playing the Reagan card. "Part of negotiating," he explained, "is so that somebody doesn't become too comfortable in their view and ability to predict you. One of the reasons [Reagan] won the Cold War was that he was a little unpredictable. It had an impact." To persuade Teheran to abandon uranium enrichments, "it has to be Ronald Reagan-like clear" that the US will not tolerate a nuclear-armed Iran.
That is actually a pretty inaccurate characterisation of Reagan's approach to foreign policy. But it neatly reprises Richard Nixon's notorious "madman theory", that Soviet leaders would be more likely to embrace d'tente if they thought that not doing so risked an over-reaction by a half-loco president.
Applied to cleaning up the mean streets of New York, this approach worked pretty well (though it eventually ended in overkill). How well it can work as foreign policy today is another matter. For my money, there are quite enough unpredictable leaders out there already. We don't need one more."