Obama to Romney: ‘We have one president at a time'

— -- President Barack Obama scolded Mitt Romney and his campaign late Tuesday for violating the unwritten rule that American politics stops at the water's edge by criticizing him overseas.

"I would point out that we have one president at a time, and one administration at a time," Obama said as he wrapped up a trip to Mexico centered on a summit of the Group of 20 nations.

"And I think traditionally the notion has been America's political differences end at the water's edge," the president told reporters, echoing a message from Republican Sen. Arthur Vandenberg in the 1940s.

( Vandenberg had urged Americans "to unite our official voice at the water's edge" to achieve "maximum authority" against the country's enemies. However, the senator had also affirmed that foreign policy "must be totally debated," though not for partisan gain, but to forge a consensus.)

Top Obama aides bristled recently when an adviser to Romney, Columbia Business School Dean R. Glenn Hubbard, assailed the president's handling of the European financial crisis in the pages of the German business journal Handelsblatt. Asked about Hubbard's piece, which described Obama's policies as "unwise" and charged they "reveal ignorance" of how Europe got into the mess it's in, Obama replied: "With respect to Mr. Romney's advisers, I suggest you go talk to Mr. Romney about his advisers."

"I'd also suggest that he may not be familiar with what our suggestions to the Germans have been. And I think sometimes back home there's a desire to superimpose whatever ideological arguments are taking place back home onto a very complicated situation in Europe," Obama said.