Barack Obama's celebrated overseas trip has left the Democratic presidential candidate open to accusations of taking victory for granted, and of wowing international audiences when he should be focussing on the problems of ordinary US voters.
His Republican rival John McCain this week turned to mocking Obama's celebrity treatment and international popularity. But he also hammered Obama on a much narrower but potentially damaging flap arising from the Illinois senator's stop in Germany.
Obama "made time to go to the gym but cancelled a visit with wounded troops. Seems the Pentagon wouldn't allow him to bring cameras," quips the narrator in a new McCain television advertisement.
The controversy erupted after Obama made a last-minute decision not to visit US troops June 25 at Landstuhl Regional Medical Centre in Berlin, citing Pentagon concerns that the visit was a presidential campaign event.
Obama said he never intended to bring reporters or cameras with him, the stop had been left off the itinerary of journalists accompanying him on the trip, and his campaign points to previous unpublicised stops with wounded troops in Iraq and in Washington.
McCain's camp has insisted it is a legitimate issue and this week released a number of statements from former military officials at Landstuhl who questioned Obama's motives and judgement in not visiting the hospital. The attacks were part of a sharply negative turn by the Arizona senator's campaign this week as the White House race entered its final 100 days.
McCain hammered Obama on his "celebrity" status, comparing him to Britney Spears and Paris Hilton, blamed him for surging petrol prices in the US and openly questioned his motives for advocating a pullout of US troops in Iraq.
Obama "would rather lose a war in order to win a campaign", McCain told supporters last week as Obama was on a tour of the Middle East and Europe.
Considered a maverick within his own conservative party and an honest, bipartisan broker for nearly 30 years in Congress, McCain's recent comments and ads prompted a flurry of criticism from US media outlets.
Some Republicans have worried that an overly negative strategy could harm his generally positive image among moderate voters.
McCain "needs to begin telling the American people how he intends to lead us. That McCain exists. He can inspire the country to greatness," John Weaver, a former McCain campaign strategist, told The Atlantic magazine. "For McCain's sake, this tomfoolery needs to stop."
But McCain's camp sees an opening, charging that Obama's trip abroad demonstrated an arrogant and presumptuous side to the Democratic candidate. They criticised his speech to 200,000 people in Berlin and argued that strong international support is no qualification to be president of the US.
Campaign manager Rick Davis told reporters on Wednesday that Obama had openly encouraged his celebrity image, "a unique facet in Barack Obama's campaign that is unlike any other campaign we've seen in modern political history."
Obama's campaign fired back with its own television ad on Thursday, saying "desperate times call for desperate measures" and launching a new website that chronicles media and even Republican criticism of McCain's new attacks.
"John McCain, who started off talking about running an honourable campaign, has fallen back into the predictable political attacks, the demonstrably false statements," Obama said at a rally in Iowa on Thursday.
Obama has made his own sharp and simplified criticisms of McCain's policies. A common refrain has been that McCain is running for the unpopular President George W Bush's "third term," ignoring McCain's independent-minded reputation within the centre-right Republican Party.
"Every candidate says, 'Lets stay above the belt,' ... and none of them do," said Roland Martin, a Chicago talk-show host and CNN contributor.