Leading article: America has finally woken up to President Bush's 'big mistake'

The United States, for all its claims to stand for innovation and mobility, is not a country that violates its conventions lightly. So it is a measure of the gravity of the Bush administration's current troubles that two especially hallowed White House conventions have been broken within the week.

President Bush, touring Asia, has transgressed a cardinal rule of national diplomacy: that travelling politicians leave party politics at home. It is not just a breach of etiquette, but unpatriotic, to badmouth the opposition when abroad. Yet, even so far from home, President Bush has used every opportunity to repeat the harsh criticism of Democrats over Iraq that he began on Veterans' Day at home.

Bill Clinton, meanwhile, has finally broken the unwritten rule that past presidents never criticise incumbents. He came close to blaming the administration for the lackadaisical response to hurricane Katrina. And he has queried the aftermath of the Iraq war in the past. But this week he went all the way, damning the war in Iraq - and not just the grievously mismanaged occupation - as "a big mistake".

That presidents past and present should now be conducting the Iraq debate abroad illustrates just how sharp the differences have become at home - and just how much is now at stake for Mr Bush. Compared with Europeans, Americans were slow to appreciate all the risks bound up with the Iraq adventure and even slower to blame the administration when things started to go seriously wrong. The public backlash is now as virulent as they come.

This was the week that the drip-drip of American doubts spilled from the margins into the mainstream. It threatens to engulf the Bush White House in a torrent. As recently as this summer, the US anti-war protest consisted of the film-maker, Michael Moore, a small clutch of ardent anti-Bush intellectuals, and an encampment of mothers mourning sons who had been killed on active service in Iraq.

Now, Mr Bush is fielding accusations that he misled the country - and Congress - into a war that was wholly unnecessary. A senior Democrat congressman and Vietnam veteran has called for the immediate withdrawal of US troops on the grounds that they are doing more harm than good. On the Republican side, Senators John McCain and Chuck Hagel, also Vietnam veterans, have publicly challenged the prosecution of the war and its effect on the image of the United States abroad.

Simultaneously, the White House is engulfed in a scandal about who ended the career of a CIA agent by leaking her name to reporters. The Vice-President's chief aide resigned after being indicted. Mr Bush's popularity rating, at 88 per cent after the 11 September attacks, has fallen below 40 per cent.

It is an uncanny feature of second-term US presidents that it is not just their first-term mistakes that return to haunt them, but character flaws that were evident before their election. Richard Nixon was brought down by his tricksiness; Ronald Reagan's presidency was tarnished as a consequence of his short attention span; Bill Clinton's as a result of his promiscuity. Now the debacle of Iraq is exposing George Bush's flaws for all to see: his superficiality, his misplaced self-belief, his vindictive fury when cornered.

Already more than 2,000 US servicemen have paid with their lives for George Bush's "big mistake", as have many, many more Iraqis. If Americans are now calling Mr Bush to account for their country's most costly foreign intervention since Vietnam, more strength to them. They have woken up not a moment too soon.