For months American critics of the war have been muttering about “another Vietnam”. President Bush’s decision yesterday to make lessons from Vietnam the core of his argument for greater American patience in Iraq was politically audacious. Politicians do not raise that ghost lightly. But he did so because it was public opinion at home that accelerated, with fateful consequences, the US withdrawal from Vietnam; and public opinion could play the same forcing role in Iraq. American opposition to the Vietnam War peaked with 1968 Tet Offensive. Militarily, it was a great defeat for Hanoi, as it immediately admitted; but politically, nothing could shake the American public’s determination to get out.

The key question is how public opinion will respond to the better news out of Iraq. No day passes without explosions and more deaths, and in the British sector, the situation in Basra is perilous. But in central Iraq, America’s military “surge”, combined with a counter-insurgency strategy that gives priority to the protection of Iraqi neighbourhoods, has begun to pay off.

As General David Petraeus and his commanders underline repeatedly, it is too soon to say whether local and tactical successes point to an enduring trend. Yet in areas of Iraq such as Anbar province, until recently rootedly hostile, there is now a semblance of order based on cooperation with US forces. The flow of local intelligence has improved, support for al-Qaeda is down and so is the number, though not the ferocity, of suicide and mortar bomb attacks. In Baghdad itself, where the rate of sectarian murders has halved, the annual Shia mass pilgrimage to the Kadhimiya shrine, marred by terrible carnage in previous years, passed this month without incident.

The Iraqi military’s numeric strength, discipline and will to fight are much improved. The Iraqi police are another matter, corrupt and heavily infiltrated by Shia militias. But in many Sunni areas where the elders have switched sides, security is assured by local “Guardian Forces”, paid by the Americans but required to pledge their allegiance to the Iraqi Government. Even if, as expected, al-Qaeda goes all out to sway American opinion with spectacularly bloody attacks in the weeks leading up to General Petraeus’s date with the US Congress next month, he will have genuine progress to report.

His civilian counterpart, Ambassador Ryan Crocker, will have no good news. Iraq’s political paralysis is all but absolute. Since August 1, when the main Sunni political bloc stormed out to protest against the Shia majority’s refusal to share more power, Iraq has in effect had no government. President Nouri al-Maliki has lost the support not only of the Sunnis and secular politicians, but also much of the country. Iraqis are bitterly disillusioned. The Americans are hugely frustrated, above all at the failure to pass all-impor-tant laws on sharing oil revenue or the rehabilitation of minor Baathists in the Saddam regime.

President Bush choked back his exasperation yesterday, denying that he wanted Mr al-Maliki gone. The trouble is that, were he to go, so would the Government, risking months of administrative chaos. Fresh elections would carry similar risks. Iraq urgently needs a political “surge” to reinforce military progress, but Iraqi politics are rotted by distrust. In Iraq, the political surge may have to come from reconciliation at local level and a grassroots revulsion against violence. That there are signs of this is cause for hope, if enough Americans have ears to hear the message.