When one politician comes up with a snappy line, the expectation is that others will borrow it and make it their own at some point.
To wit: "Make America Great Again" – Donald Trump's campaign slogan, which is just half a tick off the "Let's Make America Great Again" one that adorned Ronald Reagan and George H.W. Bush's buttons and posters in 1980.
Or Trump's appropriation of Richard M. Nixon's "silent majority." Or "America First," which echoes at least back to the isolationist movement that preceded World War II.
All of that is well within what are generally regarded as the norms, and even a tribute to the predecessors upon whom political movements are built.
So why the furor over Melania Trump's lifting of big chunks of Michelle Obama's 2008 convention speech?
The answer can be found in the controversy that ended now-Vice President Joe Biden's 1988 campaign for the White House. Biden found out that making politics personal changes the ground rules.
Then a Delware senator and rising star in his party, Biden had included a starkly personal passage in his stump speech, one that made his biography a testament to the American dream.
"Why is it that Joe Biden is the first in his family ever to go to a university? Why is it that my wife who is sitting out there in the audience is the first in her family to ever go to college?" he would say. "Is it because our fathers and mothers were not bright? Is it because I'm the first Biden in a thousand generations to get a college and a graduate degree that I was smarter than the rest?"
Except it turned out that his story had been someone else's first.
Neil Kinnock, the leader of Britain's Labour Party, was known for an identical riff.
"Why am I the first Kinnock in a thousand generations to be able to get to university? Why is [his wife] Glenys the first woman in her family in a thousand generations to be able to get to university? Was it because all our predecessors were thick?" Kinnock had said during a speech delivered at a party conference in 1987.
In early days, Biden had credited Kinnock. But there were also times when he had not.
Even in those pre-Google days, Biden's copycat delivery was found out by the opposition operation of his rival, Massachusetts Gov. Michael Dukakis, and handed over to the media.
It led to more investigation that revealed he had plagiarized a paper in law school. All of which spoke to what was deemed to be a disqualifying character flaw.
Melania Trump's infraction – which may have been committed by whoever wrote her speech – goes to some of the same issues.
When a political figure is giving a testament to his or her own biography and character and values, there is far little leeway.
On the other hand, when two politicians are of the same political stripe, an echo can also be viewed as a tribute.
President Barack Obama raised eyebrows in his 2008 presidential campaign, for instance, when he used almost the exact language and Massachusetts Gov. Deval Patrick had in his 2006 race.
"Don't tell me words don't matter! 'I have a dream.' Just words. 'We hold these truths to be self-evident, that all men are created equal.' Just words. 'We have nothing to fear but fear itself.' Just words, just speeches," Obama had said.
Patrick's version two years earlier: "We hold these truths to be self-evident, that all men are created equal.' Just words. Just words. 'We have nothing to fear but fear itself.' Just words. 'Ask not what your country can do for you, ask what you can do for your country.' Just words. 'I have a dream.' Just words."
Obama later said he regretted not naming his muse, but Deval gave him a pass.
In his 2012 reelection campaign, Obama did it again with another eloquent Massachusetts politician.
"If you were successful, somebody along the line gave you some help. There was a great teacher somewhere in your life. Somebody helped to create this unbelievable American system that we have that allowed you to thrive," he said. "Somebody invested in roads and bridges. If you've got a business. you didn't build that."
It turns out that was the same rhetorical frame that Elizabeth Warren had used to great effect in her campaign to become senator from Massachusetts.
"You built a factory out there? Good for you. But I want to be clear: You moved your goods to market on the roads the rest of us paid for; you hired workers the rest of us paid to educate; you were safe in your factory because of police forces and fire forces that the rest of us paid for," Warren had said.
Warren herself had borrowed the larger concept from George Lakoff, a University of California at Berkeley professor and liberal activist who had said, "Nobody makes a dollar in this country in business without using the common wealth."
So originality is not a requisite in politics – as long as the point that is being made is a philosophical one, and not a personal testament.
In that case, as Patrick might say, they are "just words."