While Hillary Clinton and Barack Obama continue to battle for the Democratic nomination, Republican candidate John McCain is free to travel the world looking presidential.

The senator's visit to the United Kingdom was a Congressional trip, and not officially part of his election campaign.

But meeting Gordon Brown to discuss future strategy in Iraq clearly paints him as an authoritative, statesman-like figure, who is respected by world leaders.

Senator Obama, by contrast, is busy fending off questions about his spiritual mentor, Jeremiah Wright, whose sermons about the evil of white America have shocked some of his supporters.

In his speech responding to the issue, the Democratic hopeful displayed his customary eloquence and charisma. But even if it gives him a chance to shine in adversity, this is not what Senator Obama wanted.

He has strived to prevent his campaign becoming associated with the divisive issue of race in America, but has not entirely succeeded.

And while Rev Wright's comments, captured on film, would be controversial under any circumstances, the focus on them is partly a result of the hard-fought and merciless campaign being waged between Senator Obama and Mrs Clinton.

Senator Clinton, meanwhile, also bears little resemblance to a president-in-waiting.

The campaign for the Democratic nomination has seen her character, and that of her husband, come under fire from her fellow Democrats.

If the world was fairer, the Democrats would be rewarded for having two credible candidates to offer to the American people, while the Republicans would pay a penalty for only having one.

But it's not, and Senator McCain is able to sit back and allow his opponents to fight each other while he makes small talk with America's allies.

He certainly didn't put a foot wrong when quizzed about the potential fault-line with Gordon Brown yesterday - the early removal of troops from Iraq.

The senator insisted it was entirely a matter for Britain when it deployed or withdrew troops, and said all the right things about the contributions being made by UK forces.

His view is that it would be a mistake to pull troops out quickly, while Mr Brown has said he hopes to cut British forces from 4,000 to about 2,500 in the coming months.

But the reality is that Britain's military contribution to Iraq is already extremely limited. To put it in context, the US has 140,000 troops in the country.

A drastic change in Britain's relationship with the US is unlikely - no matter who wins the presidency.