Up until that moment, the story of the London trip might have been Walker’s deference to Obama. Instead, it became, in the words of an Associated Press headline, “Wisconsin Gov. Walker Refuses to Answer Evolution Question.”

Walker’s political team back home scrambled to fix things, releasing a statement saying he believes “faith and science are compatible.” But remarkably, for a man who has run for high office, Walker didn’t have a ready-to-repeat answer on evolution. His staff didn’t even know his views before drafting the statement.

But Walker learned a few lessons. First, there’s no protection from out-of-the-blue questions. Second, Republicans, as Webb suggested, get special treatment when traveling abroad. And third, it doesn’t matter if a candidate wants to talk about cheese and industrial sand, he’s never the one setting the agenda.