Barack Obama is beginning to resemble the man who turns up to a fancy-dress party in a suit while criticising everyone for what they are wearing: lipstick, fish wrappers or, maybe, the mantle of change.

At the end of the Democratic convention in Denver two weeks ago his campaign thought that they were dressed for every occasion. Chastened by the summer's sneers surrounding his celebrity status, they decided it was time to dim his dazzle a little by donning more sober and serious apparel.

Mr Obama chose Joe Biden as his running-mate rather than more exciting alternatives because he expected the Republicans to attack him over a lack of weight and experience. In place of all those glitzy mass rallies, there would be lots of worthy speeches on policy. The Democrats did not see Sarah Palin coming, have been caught badly off-balance and are still struggling to regain their stride. Mr Obama, who had taken it for granted that change is a word that should belong to him, appears bewildered by a turn of events that has left his campaign in danger of being outflanked on home turf.

For all his talk of the “Audacity of Hope”, the only really audacious decision he has made was to launch a bid to become America's first black president. Since then his campaign — despite tactical brilliance in the Democratic primaries — has usually been strategically cautious.

This tendency has been underlined in recent weeks as Mr Obama tracked back to the centre on policy issues, softened the sharper edges of his own exotic appeal and generally pursued a risk-averse front-running campaign.

In a year when polls indicate that four fifths of voters are yearning for a new direction this has left an enormous hole that Mrs Palin is filling in a way that no vice-presidential candidate has done before. The author and columnist Camille Paglia says that the Alaska Governor represents a “new style of muscular American feminism” with hints of Madonna's “dominatrix persona of high-glam Marlene Dietrich” and Annie “Get Your Gun” Oakley, a brash ambassador from the country's pioneer past. Mr Obama is now locked in the tightest of fights with the Republican self-styled “team of mavericks”. By most objective criteria he is still favourite to win and there is little sign that his supporters' enthusiasm has significantly diminished or that this should be anything other than a Democratic year.

The largely synthetic row over whether he called Mrs Palin a pig or Mr McCain an old fish suggests that Mr Obama is not the type you would pick for a scrap. He is more at home pointing the audience towards a slightly emphemeral vision of the future or crafting the reflective paragraphs befitting a former constitutional law professor.

Sometimes he seems no more effective at attacking opponents than he was at pretending to be a man of the people by going to a bowling alley - where his first balls ended up in the gutter. At the very least, the lipstick-on-a-pig comments ensure that another day goes past when Mrs Palin dominates the stage and Mr Obama's efforts to switch the focus of voters to the “real choice” facing them prove to be in vain.

At worst, they may encourage the flight of more white women voters from the columns of undecided into the McCain-Palin ranks — a reason why Democrats were muttering again yesterday that Mr Obama should himself have picked a white woman as his running-mate: Hillary Clinton.

Times Recommends

• Both sides blame US for worsening relations
• Stieg Larsson: losing the plot over his cash
• Odd creature paralysed by incompatible parts