The first and most obvious reason for optimism is the confirmation of Tuesday’s elections that democracy works. Republicans lost not because the American people have suddenly seen the wisdom of the collective leadership of the European Union or the editorial pages of the world’s press but because they deserved to lose.

When you foul up as comprehensively as this Administration and Congress have done for six years you need to spend a period of time contemplating politics from the other side. The recent debate on these pages about whether Iraq was a bad idea in origin or just badly executed has been entertaining but jejeune from a political standpoint. It is literally impossible to know whether it was misconceived because what is absolutely certain is that is has been almost miraculously mismanaged from the moment Baghdad fell.

When you throw in “Heckuva Job” Katrina and a Congress that has devoted most of its time to enriching itself at the expense of every principle and value it was supposed to hold dear, you wonder why anyone even doubted that the good common sense of Americans would demand a change.

The second reason for optimism stems from a deep faith in the genius of the American Constitution. The Founding Fathers devised the Constitution the way they did for a very good reason, They were — and their successors today are still — deeply suspicious of rule by a single faction. They like divided government. In 31 of the past 50 years America has had a president of one party and at least one House of Congress controlled by the other party. The republic has survived. It used to be conservatives who wanted to see executive power dissipated rather than multiplied by the legislative. But, egged on by raging extremists on radio and the blogosphere they will apparently settle only for total power these days. Count me out.

The third reason for optimism is that Americans rejected not just incompetent and corrupt Republicans this week but all sorts of nonsense. The ugly call to nativist sentiment was rejected in many places, not least in Arizona, on the border with Mexico, where two prominent leaders of the anti-immigration movement were beaten.

More important, the elections endorsed a shift in the Democratic Party. A remarkable number of the Democrats elected this week are anti-abortion and pro-military. There was some bad news — the new Congress will have a markedly more protectionist hue; Democrats haven’t been completely cured of their instincts that they know better than markets how to run things but progress has definitely been made.

Now, let me end on a contrarian pessimistic note. Much of the world’s glee this week stems from an assumption that the election will force the US out of Iraq and away from the Bush Administration’s goal of pushing the Middle East towards reform and democracy. There’s a lot of talk around that the grown-ups have taken over foreign policy again in Washington. The return as Defence Secretary of Robert Gates, who served in the first President Bush’s Administration in the early 1990s is seen as a sign that the beleaguered son is reverting to his father’s hard-nosed pragmatic world view.

It follows the news that James Baker, the first President Bush’s Secretary of State, is about to recommend a sharp change of course over Iraq which involves talking to Iran and Syria, and possibly drawing down the US deployment in Iraq.

Behind all this is a sense that the US is getting ready to quit. And that’s the reason for pessimism. If the midterm elections force America to give up on Iraq in its current state it will be a catastrophe. Leaving Iraq to the nihilists and murderers who want to establish the rule of unreason in the heart of the Middle East may make short-term political sense. But it represents not realism and maturity in foreign policy but a capitulation to fear and isolationism.

If the US really has chosen to go that route, it might have been better to leave Saddam alone to practise his own form of justice and never risk facing ours.

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