Not since Bill Clinton was returned to the White House for a second term a decade ago has the British left found much to cheer on an American election night. Maybe it was this long wait or maybe it was the feeling that, even if it had taken too long coming, George W Bush had been delivered such a justly deserved rebuke, which made the results of the mid-term elections so sweet.

In the light of the Democrats’ victory, we must all hope for a more intelligent, subtle and effective approach to world affairs in general, and Iraq in particular, from the Bush administration. The days of ‘bring it on’ and ‘who’s next?’ could just be behind us.

Two notes of caution should, however, be sounded. First, while there is no doubt that the Democrats capitalised successfully on a justifiable feeling that the conduct of the Iraq war has gone horribly wrong, their victory does not offer a mandate for any particular course of action. This is principally because, split between those who supported and opposed the war, the party is unable to agree upon one.

Second, it is important to remember that, thanks to the workings of the US constitution, President Bush may be a lame duck domestically, but, on the world stage, his presidency has life left in it yet. The challenge for the Democrats will thus be to make common cause with moderates in Bush’s own party – as well as America’s allies abroad – who recognise that we need a change of strategy if the war on terror is to be conducted rather more effectively than hitherto and the situation in Iraq is to be pulled back from the brink.

The political lessons of the mid-term elections are, perhaps, a little clearer. First, while much has been made of the fact that this was rather more of a defeat for the Republicans than a victory for the Democrats, we should not allow the scale of what the party achieved to be diminished. The Democrats gained more seats than they have done in any election since the post-Watergate mid-terms of 1974. On only three previous occasions in the last century – 1932, 1952 and 1994 – has a party managed to take control of both the House of Representatives and Senate in a single election.

Second, the Democrats showed, once again, that victory for centre-left parties can only be achieved by reaching out from traditional heartlands and winning the votes of new supporters. Rural, suburban and middle-income voters – all weak spots for John Kerry in 2004 – went heavily for the Democrats this time. The Democrats’ congressional majorities were underpinned by victories in north-eastern states like Pennsylvania, Rhode Island and New York which voted for Al Gore and John Kerry, but were only secured thanks to victories in those ‘red states’ such as Montana, Missouri, Ohio and Virginia which twice delivered the White House to Bush.

The hero of the hour may have been Congressman Rahm Emmanuel, who oversaw the Democrats’ campaign for the House, but Labour might do well to heed the tactics of Democratic National Committee chair Howard Dean, who has been doggedly pursuing what he terms a ‘50-state strategy’ to rebuild the Democratic party in heavily Republican states and take the fight directly to the enemy.

Third, the Democrats’ victory was only possible because the party had managed to cross a threshold of trust – which Kerry failed to do two years ago – on national security issues. Thus while exit polls showed that the Democrats led the Republicans on their traditional strong suits such as healthcare and the economy, they also led on the war on terror and Iraq.

This opening was provided in part thanks to the failures of the Bush administration, but the party’s determination to exploit this opportunity – exemplified by its fielding of a multitude of veterans as candidates – was, nonetheless, critical to the Democrats’ success, as it is to all progressive parties worldwide.

The ‘six point plan’ on which the Democrats’ won the election has much to commend it. If carried through, the Democrats’ mix of political reform and social justice (symbolised by the promise to raise the minimum wage and attend to America’s healthcare crisis), combined with an attention to the inter-related issues of security and energy independence may help to turn the anti-Republican votes of 2006 into positive Democrat votes in 2008.

The Democrats need to beware, though, of the manner in which the US electorate has punished those parties which have overplayed their hand following election victories over the past 15 years. Bill Clinton’s swing to the left after 1992 was rewarded with a Republican Congress in 1994, while Newt Gingrich’s rabidly right-wing stance thereafter was checked by Clinton’s re-election in 1996. Now, at last, Bush’s cavalier response to a disputed win in 2000 and a narrow victory in 2004 has been dealt a similar treatment. The voters have passed the Democrats the ball. Now they need to prove they can run with it.