In fact, Lou Harris speaks of it as one of his crowning achievements.
"One of the highlights of my life was helping (Lester) Pearson defeat (John) Diefenbaker," Harris told The Canadian Press in an interview Wednesday.
"I made a lifelong friend in Mike," he said, referring to Pearson by his nickname.
Now 92, Harris says he fears Canadians might not fully appreciate the prime minister who gave Canada its new national flag, medicare and old-age pension system.
He's also envious that Canada got a single-payer health system, although he hopes his country might follow suit eventually.
Kennedy appeared to appreciate Pearson, too.
The U.S. president, who was assassinated 50 years ago Friday, took an active interest in Canada's 1962 and 1963 elections.
Harris recalls that his old boss followed the Canadian campaigns closely. While attempting to appear impartial, Kennedy's disdain for Diefenbaker and preference for Pearson occasionally bubbled to the surface.
"He was all but shouting from the sidelines," Harris said in an interview from Florida.
"He hated Diefenbaker.... He obviously couldn't say anything publicly. But every day or two he would want to know how the election was going."
There were deep political differences pitting Kennedy against Diefenbaker — such as whether nuclear warheads should be stored in Canada, and whether Canada should join the Organization of American States.
But one personal peeve stands out in Harris' memory.
He said Kennedy was particularly furious at the Conservative prime minister for making him plant a tree at a ceremony at Rideau Hall in Ottawa — despite knowing he had a back condition.
That strenuous burst of exercise wound up re-igniting Kennedy's debilitating back problem.
So for a variety of reasons the president was favourably disposed when Harris came to him with an offer to help out Pearson's Liberals.
Harris recalls that he'd been approached by Walter Gordon, the Liberals' campaign chairman, and Keith Davey, a budding organizational star who later became a senator.
Kennedy had refused a request for his pollster to get involved in a British election.
But he said yes this time.
Harris then made multiple trips to Canada during the 1962 and '63 campaigns, hiring 500 women to make phone calls in the most elaborate public-opinion research project in Canada's political history.
He kept his role as quiet as possible.
Harris says he used a fake passport, produced with the help of some friends in the U.S. government.
He went by the name Lou "Smith" — his mother's maiden name.
And that's about all he'll reveal.
Asked whether Kennedy played a role in his ability to get a fake U.S. passport, he replies: "I'd rather not get into that."
Harris says he's still planning to write a book, and is saving some details for that project.
Among the things he'd like to keep to himself, for now, are details of the polling techniques he introduced to Canada.
Some former Pearson aides interviewed in recent days said their U.S. ally helped them look beyond the so-called "horse-race" numbers and gain a broader understanding of how voters felt about issues.
U.S. polling at that time had also undergone a methodological revolution aimed at more accurate sampling.
That revolution away from the old "quota" system toward more complex random sampling was spurred by the embarrassingly inaccurate poll results of the 1948 presidential election.
David Moore, author of "The Super Pollsters," says the industry was devastated by that U.S. election — with even corporate clients, outside the political realm, becoming wary of spending money on research that could be wildly inaccurate.
Harris was part of that generation of reformers.
"I might argue the single biggest shift in the science was in the recognition of the value of probability sampling (random sampling)," Doug Anderson said in an email. He is a senior vice-president at polling firm Harris-Decima, whose ownership stems in part from the company Harris founded.
"I believe Lou embraced this and was among those who ensured it became the standard rather than innovating it per se."