When Bobby Jindal went to the U.K., he claimed that there were areas of Britain that the government had effectively ceded to radical Muslims. Unsurprisingly, that turned out not be true; more surprisingly, he refused to concede that there was no evidence for his claim.

And then there was Mitt Romney, whose 2008 tour through the continent was really more like Spinal Tap, with marginally fewer deceased percussionists. At the start of the trip, he managed to alienate even the British, America’s closest and most tolerant allies, by questioning their preparation for the London Olympics. Next, he was roundly attacked for comments on Palestinian culture he made while in Israel. In Poland, he met with Lech Walesa, only to be attacked by Solidarity, the union Walesa once led. “What about your gaffes?” a Washington Post reporter memorably shouted at Romney. He didn’t reply—but then what was there to say that hadn’t already been said?

It’s enough that CNN referred to “the curse of London.” Not everyone stumbles quite so badly—you’re just not as likely to hear about it. Marco Rubio visited, too, though back in December 2013, before he was a candidate for president. That visit was received fairly quietly, but generally politely. (Rand Paul also visited London, but, uh, not that one.)

One big danger in the trip is embedded in the purpose. The goal is less to make concrete connections overseas—though that’s useful—than to imbue a candidate with gravitas, especially if he’s a governor without much foreign-policy experience. But once a politician gets there, reporters are eager to ask questions about the trip and what they think about the world. Perhaps the smartest course for a candidate is to offer solid but anodyne answers and try to make few waves. (According to this rubric, Walker simply erred in being too cautious.)

Not every trip is so fraught—consider the rapturous welcome Barack Obama received when he delivered a speech in Berlin in July 2008. But Obama had several advantages. For one, he’d traveled abroad a fair amount and was a member of the Senate Foreign Relations Committee, so he had less to prove.

For another, his politics made him much more welcome. That’s a challenge for every Republican who travels across the Atlantic—in most of Europe, the GOP is simply far to the right on most issues, so Republicans find fewer natural allies. Even in Britain, where the Conservative Party is in power, the Tories are to the left of the Republican Party, and Prime Minister David Cameron is unusually close to President Obama. On a continent where a strong social safety net is a given, a party that has railed against it for decades faces an uphill battle. Hawkish foreign-policy stands also don’t go over so well. (Already, European foreign ministers are thought be more or less tacitly supporting Hillary Clinton.)