In the spring of 1948, Arthur Vandenberg was a powerful Republican senator from Michigan with ambitions of unseating a vulnerable Democratic president, Harry Truman, in November of that year.
Vandenberg had considerable influence as head of the Senate Foreign Relations Committee at a moment when the U.S. was reordering a beleaguered world still emerging from the ashes of World War II.
Working closely with the Truman administration, he proposed and won overwhelming Senate approval for his Vandenberg Resolution, which called for the U.S. to pursue collective security arrangements, a move that helped set the stage for the establishment of NATO a year later.
Vandenberg dropped out of the presidential race a few months later. Still, his bipartisan spirit on foreign policy and national security endured and was encapsulated in his most memorable line: "We must stop politics at the water's edge."
With few exceptions, Republicans and Democrats have heeded Vandenberg's words for generations. Congress has consistently deferred to presidential prerogative when it comes to foreign policy.
This notion was all but shattered in the past week. First, House Speaker John Boehner bypassed the White House and invited Israeli Prime Minister Benjamin Netanyahu to speak to Congress. The Israeli leader gave a blistering speech detailing his many objections to the current trajectory of the nuclear negotiations between Iran and six world powers, including the U.S.
And Monday, 47 Republican senators signed an open letter to the Iranian leadership saying they were unlikely to honor an agreement signed by Obama after he leaves office.
"I urge (Republicans) to stop the politics at 'the water's edge,'" Debbie Stabenow, a Michigan Democrat, said on the Senate floor Tuesday. "I don't believe Senator Vandenberg would have become pen pals with a group of extremists whose stated goal is death to America."
A deal on Iran's nuclear program remains hypothetical. Deadlines have come and gone and many sticky issues remain.
But the mere prospect of an agreement has opened a huge partisan divide, with Obama seeing it as the best way to keep Iran from getting a nuclear bomb and Republicans seemingly unanimous in viewing it as a bad deal.
The Iran dispute also raises the larger question of whether this will become the norm for divisive foreign policy issues.
Particularly striking has been the Republican willingness to reach out directly to foreign leaders. In one case it was the closest U.S. ally in the Middle East, Israel, and in the other, a bitter U.S. rival for decades, Iran.
There have been plenty of differences in the past, from the Vietnam War to the 2003 U.S. invasion of Iraq. But several Senate Democrats said they never considered writing to Iraqi dictator Saddam Hussein as part of policy differences with President George W. Bush.
Norm Ornstein of the American Enterprise Institute told Foreign Policy there was no real precedent for Monday's Senate letter. Richard Nixon's presidential campaign tried to stop peace talks on the Vietnam War in 1968, and Republican Senator Jesse Helms sent aides in 1979 to oppose negotiations that would turn white-ruled Rhodesia into black-ruled Zimbabwe the following year.
"But that was on such a smaller scale," Ornstein said.
Some argue that Vandenberg's notion is outdated in a media-saturated world where it's no longer expected for countries to speak with one, unified voice.
"Politics must now extend beyond the water's edge not because conservatives wish to cripple administration efforts to defend American interests ... but because they want Obama to start behaving like someone who believes in his nation's cause," Jonathan Tobin, a strong critic of Obama, wrote last year in Commentary.
One final note. While most Republican senators signed Monday's letter to the ayatollahs, a few declined. One was Bob Corker, the Tennessee Republican who holds Vandenberg's old job as head of the Senate Foreign Relations Committee.