You know, because Obama never attacked George W. Bush on his foreign policy when he was president.

LOS CABOS, Mexico — President Barack Obama warned Mitt Romney and his advisers to not attack him on foreign policy, telling the press here that “we have one president at a time.”

Asked about a Romney adviser’s op-ed in a German newspaper last month critical of Obama’s economic plan, Obama argued that there’s a history of not letting domestic politics intercede in international conversations.

“I would point out that we have one president at a time and one administration at a time, and I think traditionally the notion has been that America’s political differences end at the water’s edge,” Obama said, speaking at the end of his two-day conference with world leaders here.