I hate to break the news, but quite what is happening in Iraq is not exactly clear. We know a few things. There is a marked decline in sectarian violence and civilian deaths. The rate of murder and mayhem is now roughly where it was in the first months of 2006. At the same time, before you get too excited, we are at the peak of US troop presence, with some 175,000 now in the country.

Those of us who argued that the fundamental problem with the Iraq occupation was insufficient man-power can take some sliver of solace from this. But perhaps not for long: the troop levels will very soon start to decline and by next spring the sheer metrics of troop redeployment will mean a big withdrawal.

Will the violence resume? Will the civil war take off again? No one knows. What we do seem to know is that the Iraqi leaders, especially the Shi’ite-dominated “government”, have a few months at most to strike a national bargain over the constitution, oil revenues, the military and police force with minority Kurds and Sunnis. From everything we can tell, they won’t. Then what?

This would be a good question for John McCain. He was one of the very few Republicans to pull off a national security hat-trick: he supported the war in Iraq, he subsequently became a ferocious critic of the feckless occupation, and then full-throatedly backed the “surge”. There aren’t many people on the national scene who did all three.

Most observers honest enough to do the first two looked at the troop levels General David Petraeus was proposing and didn’t think it could be done. It’s still unclear, for that matter, what has been done. Is the decline in violence a function of the Anbar tribes’ decision to turn on Al-Qaeda – something they decided before the surge? Is it related to the dramatic ethnic cleansing, separation and exile that have occurred in Iraq these past two years, thus making ethnic friction and violence less necessary? Is it a function of the Shi’ite militias simply waiting the Americans out? Or is it a result of competent counter-insurgency policies enacted for the first time since the invasion? I’d say some as yet undetermined mix of all of the above. But the answer does matter, especially for McCain and the Republicans.

It matters because McCain offers the Republicans a way to support a still unpopular war and maintain a scintilla of credibility on national security. Mitt Romney, Rudy Giuliani and Fred Thompson have all punted on the issue of Iraq to some degree or other in the campaign so far. None will directly attack President George Bush, since he is still a semi-religious figure among the Republican base. All support the surge for now, but none has detailed what they would do next year, let alone the first year of their own potential presidency. We know Giuliani wants to bomb Iran. But we know little else.

Which leaves McCain. Yes, he’s still out there. His disappointing past six months have had one beneficial effect: he has stopped being too cautious, resumed his habit of talking nonstop to any hack within hearing range, and put his mother on television to have a go at Romney.

I loved his response to the somewhat staggering news that the Christian right’s Pat Robertson had now joined Giuliani’s campaign: “I’m speechless.” Well, when two oddballs gather together – one who blamed feminists and gays for causing 9/11, the other who hounded ferret owners as mayor of New York City – silence is often golden. McCain has even attacked Senator Hillary Clinton for securing federal funds for a Woodstock museum. It may be 2007, but you can still run against hippies.

McCain, however, looks better not just because he has stuck to his pro-war position while acknowledging painful reality, but because the others have increasingly looked so unnerving. Romney’s plastic demeanour and say-anything style have not caught on outside the first two states where he has poured millions of his own money into blanket television advertising. Thompson has yet to seem a viable president. Giuliani’s bizarre personal quirks and all-purpose, random hawkishness do not calm nerves in a very unstable world. Fellow Republican candidate Mike Huckabee is a jovial inheritor of Bush’s spend-like-Jesus conservatism, but has zero foreign policy experience. And so . . . we come back to McCain.

It’s obviously his turn. He was runner-up in 2000 and a loyal Bushie (through gritted teeth) in 2004. He’s more reliably pro-life than any of the other big names; he is extremely well versed in foreign policy; and his integrity on the detention and interrogation question makes him the sole Republican president who could reassure the world that the US will not continue to torture prisoners. He’s also able to appeal to independents in a way no other Republican can – except Rudy on a very good day.

The polls are beginning to reflect this reality. McCain does better against Clinton in hypothetical match-ups than any of the others. The latest Fox News poll finds 47% think McCain “says what he believes”, while 39% think he says what he thinks will get him elected – an eight-point honesty advantage. Giuliani has a three-point deficit on the same score. And 57% say McCain is “honest and trustworthy” – including half of Democrats and 60% of independents. Among Republicans, McCain has moved into second place nationally for the first time since the summer.

The odds against McCain are still high. But he is not unimaginable as the nominee. It’s worth recalling that in December 2003, at about this time in the primary cycle, John Kerry had a national rating of 4%. If one establishment Vietnam vet can come back from the political dead to win the nomination it can happen again.

McCain’s positions on the war, moreover, even when they have been mistaken, have always been honest and responsible. The New York Times columnist David Brooks summed up his moments of opportunism thus: “There have been occasions when McCain compromised his principles for political gain, but he was so bad at it that it always backfired.”

He is also the sole Republican who candidly believes climate change is real and Americans have a duty to deal with it. Translation: he seems in touch with the reality most Americans now accept.

But to me, what McCain offers is something deeper than any of this: honour. This man knows the price and horror of war and its occasional necessity. If McCain is president, no military prisoner will be tortured, and no debates will be had over the precise terminology of torture either.

If McCain is president, many supporters of the other party will actually listen again to a president with an open mind. If McCain is president, there will be no quarter given to Islamist terrorists, but there will be no denial of reality, false pride or contempt for allies either.

And if McCain is president, it is conceivable that a Republican could end the war in Iraq without dishonour or panic. I don’t think that could currently be said of any of his rivals.

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