As regards the itinerary, at least, Mitt Romney's trip was everything a Republican nominee's first overseas tour might be expected to be. It followed a standard route of friendly countries – from Britain, to Israel and, yesterday, on to Poland – with plenty of opportunities to burnish the candidate's foreign policy credentials and set him up as a warmer friend to America's allies than Barack Obama has been.

Insert Mr Romney himself into the mix, however, and the result has been anything but presidential. Casting doubt on London's ability to host the Olympics successfully was not only mean-spirited (particularly from a man who staged the Games himself in 2002). It was also grossly impolitic, prompting a set-down from the Prime Minister, a swipe from the Mayor and a slew of rude headlines. Not a good start.

Nor was the candidate's stay in Israel free from upset. First came confusion over a fundraising breakfast, initially scheduled for a Jewish holiday. Then an aide said that an Israeli strike on Iran was a decision that would be "respected". Mr Romney tried to distance himself from the remark, but there were comments of his own – describing Jerusalem as the "capital of Israel", for example – that were hardly less ill-judged. Whether a heavy-handed pitch to the US pro-Israel lobby, or just plain ignorance, neither is the mark of a statesman.

And now on to Poland, where there is scope for more trouble still. Mr Romney may be hoping to exploit Warsaw's slightly sticky relations with President Obama over delayed plans for a missile defence system. But his full-throated Cold War rhetoric – describing Russia as the US's "number one geopolitical foe" – may prove less than welcome in a country increasingly keen to soothe relations with its neighbour.

The striking comparison here is with George W Bush. Even the bumbling, gaffe-prone Dubya appears diplomatically agile next to the supposedly urbane Mr Romney. As nominee, he has talked tough on everything from China's currency policy to the arms limitation treaty with Russia. Such bombast is fine for the campaign trail. But to be president, he must learn to speak with more circumspection on the world stage.