When Republicans chided President Barack Obama for shaking hands earlier this week with Cuban President Raul Castro, the White House complained that the critics were breaking protocol.
"There used to be a pretty important principle that originated in the Republican Party, I believe, that partisan politics should stop at the water's edge," Deputy White House Press Secretary Josh Earnest said.
But 200-plus years of U.S. history show that the oft-invoked adage is seldom true.
"The parties have been fighting over foreign policy for as long as the U.S. has been in business," said James Lindsay, the senior vice president at the Council on Foreign Relations and the author of the blog The Water's Edge.
He points to a squabble among the Founding Fathers after the new democracy's first president, George Washington, decided to declare neutrality in 1793 in the war between England and France. That caused divisions between Washington and Alexander Hamilton on one side and Thomas Jefferson and James Madison on the other.
The saying is meant to signal that when it comes to foreign affairs, political backbiting between the parties is set aside to show a united front.
But "that part of politics, where the parties fight and accuse the other of doing bad things overseas, that's been around a long time," said Lindsay, who served on the National Security Council during the Clinton administration.
In Obama's case, the president drew scorn from Republican lawmakers when, at a memorial service Tuesday for former South African President Nelson Mandela, he greeted Castro, the president of the U.S.'s Cold War-era nemesis, with a handshake and pleasantries. The U.S. and Cuba haven't had formal diplomatic relations since 1961.
"Nauseating and disheartening," Rep. Ileana Ros-Lehtinen, R-Fla., said of the exchange. Sen. John McCain, R-Ariz., likened it to British Prime Minister Neville Chamberlain's pre-World War II handshake with Adolf Hitler.
The White House called the criticism unfortunate and said it reflected "an important progression in a number of politicians' views" on the water's edge adage.
"The White House, whether Republican or Democrat, is always going to criticize criticism of the president," Lindsay said. "Politically, it's a useful way of getting the upper hand, because what it implies is that the other guy is not being consistent with American values."
Obama campaign advisers offered similar complaints last year, ripping Republican presidential hopeful Mitt Romney's campaign for criticizing Obama's foreign policy in a German newspaper.
Some say it's unseemly to criticize the president when he's abroad. But Lindsay notes that in 1919, when President Woodrow Wilson was heading to France for the Paris Peace Conference, Sen. Henry Cabot Lodge was "writing letters to European leaders telling them they shouldn't do what it was that Wilson wanted to do with respect to the League of Nations."
There have been periods of comity, particularly in the decade after World War II. Historians attribute the "water's edge" phrase to Sen. Arthur Vandenberg, R-Mich., who Senate history says declared in 1947 that the Senate must stop "partisan politics at the water's edge." As the chairman of the Senate Foreign Relations Committee, Vandenberg helped forge bipartisan support for Democratic President Harry Truman's initiatives, including the Truman Doctrine, the Marshall Plan and NATO.
But the spirit of unity "wasn't very long lasting and it was very specific," said Stephen Hess, a former aide in the Eisenhower and Nixon administrations and an adviser to Presidents Gerald Ford and Jimmy Carter.
Hess, who studies the presidency at the Brookings Institution, said, "There was a certain sense of wanting to fight the war together and after that of keeping the peace."
But by the era of Joseph McCarthy and the communist witch hunts, it had largely subsided, he said.
Still, there remains a "certain residual sense of the water's edge," Hess added, depending on world events, such as the detente in the wake of the terrorist attacks of Sept. 11, 2001.
And in March 2012, House Speaker John Boehner, R-Ohio, was critical of Romney for calling out Obama on foreign policy while the president was abroad.
"While the president is overseas," Boehner said at the time, "I think it's appropriate that people not be critical of him or our country."
By Lesley Clark
McClatchy Washington Bureau